In reply to Flinticus: pretty straightforward then. Contact the police. Tell them where you stolen bike is and ask them to act on it. If you know where it is, and where the offender/suspect is, should justify a 'fairly' quick response. Depending on whether you've already given a statement to police or not, probably not but I don't know the circumstances of the theft, make sure it contains important identification facts. The suspect will then have to explain all the facts of where they've got it from. If they own it legitimately they will know all the facts. If they've purchased it innocently second hand (cos it's the nicked one) it's not your problem. The bike would be returned to you and any loss is their problem. Make sense?