Although it won't help the OP, I just want to point out that this is another reason that the one or two guys who preach doing manual configuration of an OBi rather than using the OBiTALK portal are really doing OBi owners a huge disservice. If the device is registered with the portal you can see the recent call history, and even change the configuration as suggested in biomesh's message. If you have access to an Asterisk server, you could reroute all calls through that and then use ChanSpy to listen in to calls, and/or the call recording feature to record all calls, so if the guy orders a pizza you'd have his address (I'm not saying it's legal to do that, but hypothetically speaking, if a thief steals someone's stuff, I don't imagine the original owner would be too concerned about the thief's privacy rights, and besides, they might be smart and choose not to reveal to the thief or the police exactly how they figured out where the theif lives).
Of course if the thief actually has the knowledge to do a factory reset then you are still kind of screwed (though you can still call the device's OBiTALK number and try to "social engineer" the guy into giving you his address, maybe by making him think he's won something valuable and you just need an address to ship it to, as infin8loop suggested), but I can just imagine the typical "dumb crook" plugging it in, realizing he can make free calls and proceeding to call all his long-lost friends.
