The police might get involved if you a) file a report and b) have pretty good evidence that someone has your bike. This actually happened for a friend of mine. She found her stolen (custom) bike listed for sale on CL several states away, turned out it was at some university campus. She called the local officer with whom she had filed her report, they got on the phone with the police where her bike was, and the next week her bike was delivered back to her.