Punched in the face? So you're only transported if you get punched in the face. Good to know. Yes, those are the first thoughts that came to Arthur despite just learning that he was sent back in time. "Thanks." He took Jardsam's hand and got up. "Yeah, I guess you could say that. We were just trying to stop you from ending the universe or whatever. You've got one hell of a jab you know. Did you train boxing or something?"
Yes, he is talking to the guy he was trying to kill several seconds ago in a very casual manner. But what can you do? He was just transported into the past, nothing he can do about it. No use crying over spilt milk, he always says. Instead, go ahead and find a way to stop that milk from being spilt again. And since he's in the past, he might even influence the future to make the fight for FCL easier. Maybe hide a weapon here somewhere... If he only had a weapon to hide.