I personally haven't, but my partners father has a couple of times, but that's because of him being a) picky about his food, and b) Dutch.
Although, working as a waiter, I've had to return a few dishes in my time, and some of them have pretty fucking dire reasons. One person returned a bowl of chips because they were "overcooked". Overcooked chips to me, are burnt. These were barely coloured, so any less cooking and they'd have been practically raw. The chef told me to refund them, because she wasn't happy to serve practically raw chips.
But then saying that, I can recall one time when someone's kid cut into a nugget, and it had blue inside it. Turned out that there was a bit of some kind of packing material that had been mixed up with the chicken meat mix, then formed into the nugget. Cue 2 bags of about 200 nuggets being instantly chucked (yay for having batch numbers printed on them), a refund, and a massive bowl of icecream for the kid.