Probably not this simple but can't you just buy it, get a receipt and try registering it. If your collar is felt explain that you bought it from so and so etc. etc.
Best to make sure your freind isn't planning any foreign holidays soon.
Does everyone who buys a trials bike make a note of the frame number in case it gets stolen? I know they should but how many do?
I bought the CR500 without any matching numbers but the reg fitted the description of the bike and that wasn't stolen. That was good enough for me.
Probably not this simple but can't you just buy it, get a receipt and try registering it. If your collar is felt explain that you bought it from so and so etc. etc.
If Stolen then the police will take from you and return to origonal owner and leave you with nowt