I don't condone this but could see how it could happen.
I went to A Wendy's for take out for the family. I ordered 4 Spicy Chicken Combos and drove home. When I got home I was missing one of the Sandwiches. I went back and waited and went to the drive up window. When I got to the window the person I complained to said" Oh, are you the guy who left without one of his sandwiches?"
If I had a bat I might have gone after him too.
You never, ever, leave the window, until you have made a complete inspection.
Exceptions are few.
Pal's in East Tennessee never makes a mistake.