Publicly confront him loud enough for everyone else in the joint to hear.
Invite the local TV station, or if they don’t want to show up, just get a friend with a video camera and a windbreaker to act like he’s “official”, then pop the “Thou Shall Not Steal” question on him. Post the video on Youtube and hand out flyers with the URL in front of his churck.
Better yet, if you really want to be nasty (?), send a note to his church saying there’s been an accident at the Panera and you need someone who can identify him ASAP. Then he’d be publicly humiliated in front of someone he probably respects.