Damage to engine from excessive idling?

I recently had my Ford in my local dealership for a simple Check Engine light. Although it took 3 trips to get it right, my problem occurred when I went to pick up the car.

The dealer was supposed to have locked the car and left the keys under the floor mat. (I was going to stop in later that night to pick it up.) Instead, some Bone Head decided to leave the car with the keys the ignition and idling and then went home. (Did they confuse a floor mat from the ignition?) Three hours and four gallons of expensive gas later, I picked up my car. My question is, what damage was likely done to the car and what is reasonable for them to compensate me?
Oh yeah, the same bone head left the car unlocked as well. I guess he forgot to illuminate the “Steal Me” sign.

Other than wear (minimal), there should be no problem. There is more wear upon starting a car than running for hours. Try to get the service peeps to reimburse the gas though.

-bronn