i'd be checkin all the local high schools for mud splattered vehicles (status symbol)
and since you say it's $1000 dollars worth of damage a tire tread
plaster mold should be done by the local detective.
Also the local
do it yourself car washes might be a place to do a drive by and check for a real muddy stall because maybe the attendant saw that vehicle and was pissed at how much mud mess they were gonna have to clean up afterwards.
the punks obviously don't want to scratch their car or they would have really gone off roading....
with gaffitti also on the walls maybe its time for a camera up there!