"What, were you in there when the train started moving?" Since he's lacking the context about how a suitcase falls on you randomly, without something to help in that. But he'll answer the other previous question himself, having the chance to do it: "And nah, not Osiga. Was some other place - don't remember a name."

When you get stuck in a room for a few hours and you're running around focusing on more than the actual place you're at, you don't recall a name very well. Which Tidus is only realising, any recollection for the name... nope, not coming to mind.