Probably not what you want to hear, but move on. Think about getting your replacement bike. Chalk this one up to experience, and get a better lock/chain next time or leave it in a safer place.

If you get the bike back, great, but in all likelihood, it's gone forever. I've had bikes, lights and parts stolen and vandalized, and it can be upsetting to know someone made off with your precious possessions, but there's not much you can really do about it.