Something I'm not catching on to here.....
Was the cherub identified or traced at the time or is it an ongoing enquiry? Guessing he/she was traced at the time and locked up.
If driver was 16 then he/she is (certainly up here) an adult and goes to adult Court. Under 16 then its the Childrens Reporter or Panel. Either way, still gets done.
Driving a stolen car - the stolen car should be insured by original owner and unless 3rd party only cover - rare nowadays, 3P F & T the norm - and should cover damage to yours. If not, then thats what the MIB is for. You probably have some sort of DAS or legal protection scheme with your own car insurance or indeed house insurance, so use that to get things rolling.
No prosecution? Going on the circumstances you relate, can't see why the little cherub is not getting done. Would suggest contacting the home Force and requesting an explanation of their actions as you are an injured party (or your car is) and you are intent on persuing the recovery of uninsured losses due to their (Officers) actions. Send all mail recorded and keep copies. Least that should be forthcoming is the identity of the driver so that you can recover losses. May need the payment of a fee, though..... Data Protection Act gets soddin' everywhere....