Id have to try a stake out with some bait. Check all pawn shops, Craigslist, Ebay
Ask the store clerk and police if theres a theft hot spot or try to find a place were bikes get ripped off. More then likely there watching out for you if you been there before.
Also check like if he could a been on an accessable roof and waited to hear you comming then had an escape plan real fast.
Hope you get it back.