His eyes widen when he steps out of the store and spots one of the tallest dudes he's ever seen in his life. Or, at least, probably. Sam can't really be sure, since his memory is pretty spotty. This guy is bigger than Thor, anyway, and that's saying a lot.

There's also a lot to be said about the other guy's reaction, the way he jumps and looks apologetic about it; especially coupled with the old scar and the military dress. Sam can draw conclusions based on something he actually is sure about. Before joining up with the Avengers, Sam remembers counseling war veterans, and this guy reminds him of a lot of the people he'd met in that line of work.

His surprise quickly fades and is replaced by a friendly smile as he returns the wave. "Hey man. You look kind of lost." There's a lot of that going around today, he's found. "Need any help?"