Report it the the police and get them to check the registration. It might be security for a vehicle loan in which cases you can be prosecuted for possession of stolen property.
Go to the police with any evidence you may have and explain the story to them and ask them to check ownership. Also ask then for transfer of ownership to your hands to defray holding/ storage costs and you might get to keep it. At worst they will impound the bike and its off your hands.



