This happened to another server at my old restaurant; I almost couldn't believe it.
A guy came in, carrying a birthday present, and asked for a table for three. After waiting alone for a little while, he told his server that the people meeting him were running late, but he was really hungry, so he was going to order. He orders our most expensive meal (not that it's that expensive, but still), and leisurely eats. He chats with his waitress, seems like a nice friendly guy. Eventually, he tells his server he's going out for a smoke, but would like to order a dessert. He tells the hostess he'll be right back and goes outside, leaving the wrapped birthday gift and card on the table.
Yep, he never comes back. After half an hour, his confused server goes to clear the table. When she moves the wrapped box, she notices it's very, very light ... it's empty. The card isn't sealed, and when she pulled it out, it said inside "better luck next time".
Who the fuck takes PROPS to a dine-and-dash?
(edit: check out Well Done Fillet for more shady fuckers)