On occasion it has happened to me. I try and remember to check the gas level when I get in the car. If it is below full I tell them so they can note it on the invoice. The problem is when they say, "Just bring it back with 7/8s of a tank". Yeah, right! How do I know when to stop filling the tank?!?
Last time it happened they gave me a $25 coupon for the inconvenience.