^^Yeah, he's concerned, but I think one of the things that plays into the mix of reactions is that Trip probably isn't sure how worried he needs to be. On the one hand, Phlox is telling him that T'Pol has a slight fever and that there's no need for concern, and while T'Pol doesn't seem to be physically ill/depleted, she's acting pretty weird (staring and grabbing at her food). So Trip probably thinks there's something more going on but has to coordinate finding the Captain, so he leaves it to Phlox to handle and tells him to call if needed. And that factors into the mix of surprise/shock, puzzlement, and perhaps skepticism that plays out in Trip's expressions. At least that's how I saw it....
OK, to wrap up S2, a scene from "The Expanse." Trip and T'Pol aren't even in the scene together (which may be why this one doesn't get a lot of focus as a T/T moment), but I like it anyway because I think it's well played and also because it alludes to how Trip's view of T'Pol has changed over time.
Archer and Trip are having a drink as ENT head towards the Expanse. At this point, they still think T'Pol will be leaving ENT and returning to Vulcan.
Trip asks Archer if he's picked a new science officer.
Archer indicates that he hasn't.
Trip says, "You're gonna miss her, aren't you?"
Archer says that when T'Pol was first assigned, he wanted to strangle Soval....
Trip admits that T'Pol does sort of grow on you.
Archer seems surprised and says that he thought Trip would be the first to show her to the airlock.
Trip looks on for a moment
closes his eyes briefly
and drops his head. Awwwww....