Forget the awkward smile for a second, because @the_harper gets the freeze. Here's a different angle: he put you on the spot at his job, where you're a captive audience just trying to pay. That's a bit of a power move, whether he meant it or not. You don't owe him a certain act next time just because he shot his shot. If you want to be polite, just act normal like it never happened. If you feel weird, maybe hit a different coffee spot for a bit to avoid the whole thing.