Thanks everyone. I have the GPS back in my possession finally

I met with the detective briefly and he shed some more light on the subject. He confirmed that it was a kid, aparently he has had some problem with the law in the past (nothing as serious as theft, but has a lead foot and a temper and gets into fights pretty often).
He said he was sure the kid stole it, but didn't have enough proof to make it stick, so they are just going to keep their eye on him. I asked if anyone else had reported the other stolen items he was ebaying, and he said no. I told him I almost didn't report mine, but ebay required it, he said never hesitate to report these things (no matter how small they seem), because usually the theif never just steals once, and when he finally does get caught, they sometimes have a bunch of other stolen items that the theif can't remember where he stole them from, and if no one has filed a report, there's no way to get the items back to the owners (makes sense).
I plugged the GPS in to make sure that it still worked as soon as I got out to my car, and it came right up, but somewhere along the way, someone set a Password on user 1 (will have to contact the manufacturer and find out how to reset that). Again, I'm really happy that I got this back, I never expected to see this thing again, and I can't believe I actually have it back now. Thanks again to everyone for the comments and help.