Sounds like a tyre place here in SA. I was talking to one of the guys who works there, and he says " Oh we had a GTR come in, and all the guys were drooling over it, so we all took it for a big thrash around the block, the manager even did a huge burnout / takeoff out the front.
I then said to the guy, yer thats why i dont take my car to places like yours...and i walked off.
Sounds like they possibly had a good time with your car, then hit a curb as said ^. Id be asking to speak to the manager, or owner, and pointing out you are not a moron, u know how the car was etc...I hate places like this that try rip u off. Id even ring consumer affairs to complain u didnt get what u paid for...(im a picky bastard:))