Had this happen years ago when I was working as a hostess in a nearly now-defunct restaurant.
This guy walks in, carrying a shopping bag and looking anxiously around for his alleged wife & daughter. He asks to be seated by a window so he watch for them. He waits a long while. I brought him some water and iced tea. Meanwhile he's fussing, looking out the window. Finally he says he guesses he'll go ahead and order. I don't recall what he ordered, I think it was just a burger or maybe a ribeye steak sandwich.
It was about 30 minutes later when he asked me if he could just step outside and look for them, he was worried they hadn't shown up yet! This guy was a great actor, folks. Stupid me, I said sure.
He walked off and never paid for his meal. There was no wife, no kids, and the shopping bag he left at the table was filled with old newspapers. So much for trusting people!
I had to step in the back and tell the store manager, uh, we've been scammed and I'm so sorry. He was good about it. He practically applauded the use of the shopping bag. Nice touch!!
Now here's one who didn't get away. Anyone who has ever worked in a restaurant which uses a commercial dishwasher knows the glasses go into the rack upside down. So this woman is halfway through her meal when she calls me over to her table - I was not the server, I was just seating people but I did pour her a glass of iced tea. And she exclaims, LOUDLY
"there's a screw in my glass!" She wants her meal comped, immediately! (Her friend looked a tad embarrassed.)
I smiled politely and explained to her there's no way the screw was in her glass because (1) I poured the tea myself and it wasn't there when I served it to her and (2) screws just don't fly up into glasses that are sitting upside down in a rack. It's a physical impossiblity.
So I called the manager over and he said, well, I have to agree, that screw didn't just get there on its own. She didn't get her free meal. And I'm betting her companion didn't go out to lunch with her again, either.