My Grandfather did a similar thing to a guy at work in the 60's. They worked at a sawmill and the guy on cleanup would go into the guys lunches and steal the desserts. They warned him it was my Grandfather's Birthday and not to touch the cake he had made. They came back at lunch and the guy had eaten half of a full cake. Little did he know my grandfather had handmade the cake and frosting and had used Exlax as the baking chocolate in the cake, he had an evil sense of humor, one I try to carry on.
This was before Human resources was really a thing in that industry. The guy was in the hospital for days from dehydration as he damn near shit himself to death. His wife hated them from then on, but they would joke with with the cleanup guy with pieces of chocolate all the time and he would damn near throwup, guess it cured him of stealing!