I feel like Buck was trying to get Tommy's attention after all, at least when he went to visit him to talk about piloting helicopters and all that jazz, but then when Eddie arrived with his big truck acting all giddy and Tommy greeted him like that he:
A.) Got jealous of the person arriving (we can see his face drop at the mention of the raincheck because Tommy had something else to do with someone else before Eddie is in the frame) because he wanted to be the focus of Tommy's attention and get him to light up by his mere presence like that for some reason he could not pickpoint and the person just happened to be Eddie.
B.) He then realized it was his best friend who was hanging out with another guy and not him, and was doing fun new stuff when all they, Buck and Eddie, probably do is stick to this household routine playing the little family and apparently that was not what Eddie wanted anymore. Tommy and Eddie went out to a fight in Vegas, Tommy and Eddie went out to a fun Karaoke Night, Tommy and Eddie went out to play a Basketball Game while Buck now seems like the type that only likes to go out for a celebratory beer after a good shift with the 118 and if it's plans with Eddie, he likes to go to the Diaz household and spend time there. (It's Evan "I'm not really a guest." Buckley, y'all)
So he is jealous of Tommy and Eddie together, and Tommy and Eddie separately as individuals.
Jealous that Eddie found someone else he could just click with, jealous that Tommy found another guy that made him laugh and stole his attention and jealous that they were hanging out without Buck and having a good time without him being there, ultimately making him feel expendable.
Maybe he is even jealous that this going out feels a lot like they're going on dates, and he doesn't really go out one on one with Eddie unless it's to go to the park but with Chris, and he also doesn't really know how to feel about that or why he is feeling that pit on his stomach whenever he thinks about Tommy and Eddie dating each other.
He rationalizes then that he has never felt this way around Eddie's girlfriends, so Tommy going on dates must be the reason.
So, he must be trying to catch Tommy's attention, right?
