Worm in my food!

I ordered a Reviver salad (no chicken). I waited 20 minutes for the salad, and finally after having asked where my food was twice I received the salad once all my friends had finished eating, only to find a worm in my salad. The manager was apologetic and I got my money back but it is absolutely unacceptable for there to be worms or bugs in your salad! Disgusting!