This happened to me at Papa John's. And I did ask for a replacement. My reasoning was that what was going to happen later was I was going to try to put it in a vending machine when I really wanted something, it wouldn't work, and I'd be frustrated. Then it would just go in the garbage.
I felt kind of bad though when it took a manager's assistance to reopen the cash register. My wife said she would have just left it as their tip.