Man, unlucky saurus...
The thing that shits me is the insurance companies and police act like it's our fault for leaving valuables in the car. As far as I'm concerned I can leave what the phark I want inside a lock car, if someone steals it, it their fault. I'd go as far as to say I should be able to leave it in plain view unlocked, theft is theft.
It also means most likely, someone saw you with the gps in the car/putting it away in the glovebox or just assumed it was in there?
How did they lock the GPS? does it have a SIM card in it for data?