My boys Moped was Seized by the Police after he was in collision with a car that cut him up.?

he was 15 years 10 months on the day so exactly 2 months before he could hold a provisional license,he claims to have been pushing it and there are witnesses to back him but the driver of the car claims he was ridding.It was the driver of the cars fault as she cut him up getting into her drive but because my boy had no license no insurance etc all tables turned against him,He did a very stupid thing to take it out against my advice and not wait (only 2 months) he's older mates tempted him whilst they are all legal on theirs now he's on his own?.My question is how can I get the Moped back as its only got minor damage,2 years old and not loose all the money I spent.He had not sent the Log book of as apparently a minor cannot be the registered owner of a vehicle,when I went to the Police Station the clerk said only the registered keeper could get it out,we bought it in Birmingham 150 miles away,former owner just signed the green part of the log book,I have tried calling him all in vain,The guy at the impound agreed to assist as for the storage fees but said I have to sort the paper work with the police first, Please help as time is not on my side,How do I untangle this mess?