Your order being fucked up or undercooked, or having an allergic reaction is a valid reason to have your meal comped, merely not liking the food is not a valid reason. It sucks you didn’t like it, but it’s no fault of the restaurant. That’s what you ordered. It doesn’t matter you only took two bites of it, all the restaurant can legally do with it is throw it in the trash, so it’s still a loss for them.