Are you sure the current owner is the thief? Whoever has it now might have bought it shortly after it was stolen, or might have bought it from the guy who bought it shortly after it was stolen.

If you can prove it is stolen property I guess you have every legal right to repossess it---or to have the cops do it for you---but i'd be a little leery about making accusations and assumptions.

I bought one of my bikes at a yard sale, and another from some guy I met at an MTB trail. I have no idea of the provenance on either bike besides what I was told. One or both bikes could have been stolen. I would certainly look into suing you if you slandered me by calling me a thief, or called the police and accused me without any evidence.

In any case, hope you get the bike back ... don't see why you couldn't.