Man that sucks Das, I would completely lose it if that happened. Last time I took my car into a suby dealership it came back with a 4 inch scratch in my door. Got screwed cause they said it was there before I brought it in.
I now inform anyone that take my car that they are not to drive it without my permission and they are not to take it over 5000rpm. I also lie and say I have a GPS installed that I can monitor their speed and location with(why not). I also take down my kilometers and require explanation for any additional on the car. I make myself available to go with them for any "test" drive as well.
I HATE leaving my car in other people's hands but sometimes it's unavoidable. Hopefully you hand their asses to them legally.