I've been trying to track it all down with several different methods. Now I've got this idea and found this is probably the best place to ask if it is possible.
With mobile phones you got a specific code (IMEI or something) that is detected when it connects to a radio tower and mobile operators can using that connection, track or lock the phone.
Now I was wondering if each iPod Touch had that specific code that would be detected if it were to connect to Apple website, AppStore or use an app through WiFi. If that was possible, it would probably lead to finding these crooks along with the rest of my stuff.