could contact the seller via gumtree and tell them that the owner has recognised his bike and the police are tracing the ip, and suggest that if the bike is returned to the owner or left somewhere anonymously no further action will be taken (ie agreeing to give evidence to the police as owner, victim etc which would make a prosecution impossible and no charges brought).
might work or might spook the crim and have the bike dissapear.
could contact the seller via gumtree and tell them that the owner has recognised his bike and the police are tracing the ip, and suggest that if the bike is returned to the owner or left somewhere anonymously no further action will be taken (ie agreeing to give evidence to the police as owner, victim etc which would make a prosecution impossible and no charges brought).
might work or might spook the crim and have the bike dissapear.