• do you need the police to trace an ip?

    As indicated by Kerley, most internet users these days do not tend to command their own pipe inlet/outlet backing on to the over arching system of tubes known as the main frame, so IP location e.g. tracert is mainly useless in most cases, except to perhaps a cursory identification of the ISP of the user, or perhaps of his hapless final-jump-proxy (due open ports or w/e).

    As I understand it, the most likely case would be that for any given IP address holder suspected of malfeasance; in the first instance you would need a solicitor to petition on your behalf to the ISP within which whose address ranges you allege the alleged perpetrator to have been resident at the time of the alleged action, for a court order forcing disclosure of his personal details, as per various bittorrent copyright infringement notifications sent by certain litigious law firms to many private individuals in recent times. (caveat: poor example)

    or otherwise you would need a second point of contact to the known IP address holder, in order to socially engineering or such tricksy with a to finally other ends (such as sending a masked RAT to his direction)

    In any case I wish the OP the best of luck in retrieving his bike, and apologise for the status and/or content of my post. (non-utility).