When I was a waiter, we used to get wooden coins that said “Round Tuit” on one side, and “You always said you’d go to church when you got a round tuit” on the other. Always on Sundays, when the after-church groups came in, never any other day. At least with a round tuit, you knew you were getting stiffed.
Fake money would have really pissed me off, I can’t see it being a tactic of a regular customer. That’s got to be a cruel trick that one-time-only, passing-through customers use.