What Guys Said 1
Relationships are neither made nor lost quickly, so don't worry about that.Sounds like he's going through some things. Give it time, you could always ask what's up though.
What Girls Said 1
Just ask him if something is wrong. You say he didn't come out of the room to talk, but you could've gone up to him and talk? You could call him/email/text/ go to his place and ask him if something is up because you feel you drifted apart. Just talk to him about it.