Imagine if Bilbo lost his lil acorn once Smaug was dead.
Throin sees Bilbo looking around all panicked, digging through some pile of gold or gems, and asks about it, and this is where he learns about the acorn.
So of course he offers to help look, while they're looking for the Arkenstone, and eventually they've got the whole company looking for both. Thorin's head seems a little more clear suddenly, so everyone's more looking for the acorn than the arkenstone, because yeah they're looking for the arkenstone, but they'll know it when they see it, they have to CONCENTRAIT to find a lil acorn, and it's important they find IT soon or it'll get crushed, or die or rot. The arkenstone has lasted this long. It'll last a little longer.
And because they've all got he mindset if "yeah thats a bit of gold, but it's not an acorn. Sure sure some pretty gems but it's not an acorn!" In there heads, they stave of the gold sickness.
When Fili shouts, "I found it!" They're all rather disappointing when they realise he means the Arkestone. Thorin pockets it, but they return to their search for the acorn right away.
Then, one day, Thranduil shows up demanding the white gems and Thorin's standing up on the barracks like "Sure, if we come across them."
And Thranduil's like "what do you mean if you come across them?"
"There was a dragon in the mountain for over a century! He wasn't exactly cleaning and we're a bit preoccupied with our own search at the moment! I'll send them your way once we find them! If takes a day or a year, you'll live!" And then he disappears from Thranduil's sight.
Only to reappear after a moment, looking slightly irritated. The hobbit is by his side looking, perhaps hopeful? With a roll of his eyes, Thorin says, bitting out the words like they physically hurt to say "If you would like, perhaps you could send a select few of your most trusted guard, and if they might help us in our search, they can also look for your gems as well?"
Thranduil has never been more caught of guard in his life. Did a dwarf, one whom he'd had imprissoned in his dungeon less than a month ago, just invite his people into his most recently reclaimed treasurey?
"I'm sorry. What?" He blinks up at the dwarf- most elegantly, he assures you.
"Elves have very keen eyes, do you not?" Asks the little hobbit. "We're looking for my acorn, you see, that I got from Beorn the skin changer, I seem to have lost it in the dragon's chase, and we fear it'll be crushed. Throin says your box would likely be in the front of the treasurey, and we haven't searched there yet, though Smaug did follow us through there, so it's a fine place for your people to start. It would be greetly appreciated."
And really. The argument could go on, Thranduil's really not sure he believes there IS an acorn, but if it gets him those damned white gems, fine. He sends Tauriel and her guard, and Legolas volunteers himself.
When Bard shows up asking for aid for the town Thorin throws his hands up. "Your just as bad as the elves! We just got our montain back! Fah! At least you asked for nothing so specific!" And practically chucks a chest full of randomly scooped up gold and gems over at the man. "But if there is an acorn in there, you are to return it immediately!"
"Why would there be an acorn?" He asks Thranduil that evening as he takes tea with the Elven king who's made camp outside the Lonely Mountain as a statement to the dwarven king he doesn't mean to leave without what's rightfully his, regardless of their compliance.
"His husband appears to be rather attached to it." Thranduil shrugs. "I don't pretent to understand the ways of haflings, but if the hobbit has half so strong a love for that which grows from the earth, as the dwarves do that which is mined from it, and I was a king who'd dragged my consort half way across Middle Earth to risk his life battling a dragon for its hoard, I'd think it wise to have the Mountain turned upside down for one measly acorn as well."
Dain shows up and is about ready to storm the peacefully-aiding-the-humans-at-this-point-because-we're-here-what-else-do-we-have-to-do elves on principle, but Thorin puts a stop to it quick.
It takes Dain a day and a half to realised that Thorin did infact say "they were all looking for an Acorn," yesterday, and several minutes to understand that he was saying "no, we found the Arkenstone days ago," today.
And of course, the orcs and goblins show up and are defeated by the forced of them all, united under Acorn Peace Treaty of 2942
Sadly, weeks go by, and they do not find the acorn. They do eventually find the Gems, and Legolas and the majority of the elves return to Mirkwood, Legolas having made good friends with the Company, especially Gloin (this is a suprise tool that will help him later) but Tauriel remains, and if Thorin wasn't smitten with the hobbit, he might comment on just how close Kili is growing to her. At least she's respectful. Might just teach that boy a think or two. The opposite is, of course, true, and Tauriel becomes just as much a menace as the princes.
As the weeks go by and proper cataloging of the treasury commences, every dwarf who comes to help is shows a picture of the acorn every single morning, and promised a just reward for its discovery.
Eventually, Bilbo has to concede they aren't going to find it, but, well, by then he's not exactly planning to return to the Shire for long enough to care for a sprouting tree.
He does return long enough to stop all his things being auctioned off, no he's not a ghost, thank you very much, and have Bag End transfered to his cousin Drogo and his wife, before setting back out for Erebor with the things he intends to keep.
It's years before anyone thinks of the poor lost little acorn again, decades, infact.
One day, in the early morning of the 21st Durin's day after the reclaiming of Erebor, a dwarf comes rushing from the treasurey to find the Royals preparing for the celebration.
"Is it one of these, your highne- uh, Bilbo, your lost acorn?" He asks, stuttering over the title he knows the hobbit dislikes. "I can't really.... tell them apart."
And Bilbo just blinks, because in the cupped palms of the dwarf's are perhaps 15 or 20 little acorns...
"Where did you find these?" He asks.
"The back?" Thorin repeats, then catches himself and shoos the dwarf back the way he came "Show us."
They all- Bilbo and Thorin, the princeses, and a handful of the company who'd been present- follow the dwarf down into the treasurey, and then through the treasurey, past all the neat piles of gold and the many chests of organized gems and stones and all manner of other treasures, until they're presented with a very familiar back door.
Or rather, a hidden passage, tucked away in an alcove, where another handful of acorns' the few the Dwarf who'd brought them the first had likely missed- are scattered about.
"You did... just have the one, right Uncle Bilbo?" Fili asks.
"Or course I just had the one!" Bilbo retorts. "I couldn't have possibly carried that many with me all the way from Beorn's!"
With a resigned sort of sigh, as he begins to piece together the answer to a decades old mystery, Thorin steps forward and follows the tunnel up, up, up, and out of Erebor, the others- save the dwarf who brought them, dismissed by Bilbo with a smile, a thanks, and an oh, no, you may keep those- right behind.
As they walk, the acorns start to increase. Though there's never so many as to begin piling up in the tunnel, by the time they reach the end, the majority of the ground is covered in a solid layer if the little things, and the crunch underfoot as they all emerge onto the ledge which they had all once stood, with batted breath in the moon light as they realised they were at last, truly home.
"Was that here last time?" Kili asked, studying the impressive Oaktree shading the entire ledge that sat in front of the secret entrance to Erebor.
The trunk of the tree was wide and solid, sitting right up against the mountain side, and rather winning the battle of wills against the carved stone architecture of the dwarves. Its limbs grow twisted and wild, up and out in all directions. It's easily 250 or 300 feet tall. There is all sorts of life flittering about in its florishing branches, all covered in brilliant green leaves, and fresh green little acorns.
The growned all around them is covered in acorns as well, so many more than the tunnel.
"No." Thorin says, watching a squirrel dash down from the trunk of the tree, shove several acorns into its cheeks, and dash back up the trunk. "No it was not." He turns to Bilbo, and raises an eyebrow. "Lost it after the dragons chase, you said?"
Beet red and look quite flustered, all Bilbo can manage out is a squicky little "oops."
"'Oops' indeed." Thorin returns, smiling fondly.
