This discussion may contain spoilers!
All of a sudden, Kenny's alone outside planning on how to get out of the predicament c/o Carver. He told Clementine that Luke ran off because he was whining about something. Then, after everybody surrendered, Carver said something like "if you hadn't followed that guy, you wouldn't be in this mess," possibly referring to Luke. He might just be talking BS here, but who knows?
So we see Luke again in Episode 3 infiltrating Carver's camp, as most people would have expected. But when he was talking to Clementine, he's stutters quite a lot. Even later during the episode when he was making a plan, there's even an option there for Clementine to say "Are you alright?", which is like saying "Wtf is up with you?" given the context of the situation.
SOMETHING IS STILL UP WITH THIS GUY.