couldn't you get the engine and vin nos? just find the owner and say you're really interested in buying it.. maybe leave a note like this
"Im a rich bastard that likes to spoil his kids, my son has just got his P's and wants a sklyine, as i am rich i have no idea what these cars are worth so i'll give you lots of money"
that should lure him in then go look at the car pretending to be the spoilt son, then get the chassis number then POW!