wouldnt there be paint marks on your car - eg, paint from the other car? You could put a complaint to the cops.
This happened at monash uni a few years back - some car hit a parked silvia (which was owned by someone that my friends knew) - and it left some mark on one of the mags - he went n complained to the cops, they took details, and last i heard, they tracked down the car that hit his or something.....maybe worth a try?