i used to work in a restaurant, yes stuff like that does happen when someone is a total asshole to the servers.
the worst i ever have seen was when some guy came in and was screaming at the waitress because she got his order wrong.
he ordered a hamburger and she accidentally wrote down a veggie burger.
he was being a real dick, He was screaming at her and demanding free stuff from the management. So the kitchen staff decided to take the raw meat and rub it on the under lip ---(the area covered in sprayed shit, urine, and rust)---of the filthy nasty hasn't been cleaned in weeks employee bathroom toilet. they then proceeded to cook it up to his liking.
he didn't even leave a tip. That ungrateful bastard