That is exactly the kind of thing that he, as a now-full-fledged member of the Enterprise crew, refuses to accept. Even if he turns out to be wrong.

"I need to get back to my ship. When I left, we were trying to figure out how people had wound up on board in the first place - I'm sure they're still working on that, and they'll figure out a way to establish a connection soon."

This is the Enterprise he's talking about. There's nothing they can't figure out, and his faith in that can't be shaken - nor is he ready to accept the possibility of being away from them for long.