hm.. so by your theory.. if a friend parked on your driveway, and a neighborhood kid loses control of his bike (but there were no witnesses so you don't know which kid) and crash into your friend's car, you're liable for fixing it because he parked on your private property?

this is just my opinion but that's just lame. sorry your car got scraped but what was the point of approaching your boss about it? the only thing you accomplished by doing that is piss him off. so unless there's some video surveillance to show who did it, you're $hit outta luck.