"From experience I can tell you that many times the guests DON'T hold onto their reciepts."
I bet that same experience helps prevent you from calling the police on customers who paid for their meals. What I mean is, somebody at your counter probably would have remembered taking money from the guy.
We had this group of Pentecostals who used to come in on Sunday night. They often took trips to the salad bar without paying but my boss just wrote it off. It was when they started unplugging the juke-box and infuriating the other customers who put money in there that we had to do something. About the time I plugged it back in one night and they began singing above the volume of the juke box and we had to call the cops because they would not stop.
Sometime people just refuse to act right.
Of course that only applies if he is the one that went to the counter to the counter to pay...