No, restaurant workers will not mess with your food in that way. No matter what they think of you as a client. Ask people you know who have experience in that sector and they will tell you that such things are absolutely taboo. Anybody who did anything like that even once - or even suggests it - would be instantly fired and blacklisted in the community.
If the waiters or chefs hate your guts, at most they will swear in the kitchen.
If the waiters or chefs hate your guts, at most they will swear in the kitchen.