Thinking about the Japanese tendency towards nuance and understatement and Luomen's reaction to Maomao going missing. She's his daughter, she means the world to him, he's taught her his pharmaceutical and differential diagnosis skills even though it leans towards the taboo for a woman to do so. It hits like a brick for him to dismiss her short disappearance so casually in front of a freaking-out Jinshi.
One year, with Luomen not knowing whether Maomao was alive or dead; a year of worrying and waiting, and nothing he can do about it even if he hadn't been exiled from the rear palace. Jinshi is pitching a fit about ten or so days, and meanwhile the machinery of the emperor's rear palace is responsible for the disappearances of so many young women who get picked off the streets to serve, with their own parents left to wait and worry and watch.
"One time, Maomao went missing for a year" is a deserved slap in the face for the men responsible - hey, Jinshi and fam, this time you and your retainers are concerned because Maomao is your pet House MD, and how do you think Luomen felt? Suck it up, buttercup, and maybe it's about time to rethink how things are done around here.