My wife lost her iPhone 3G a few years ago and oddly it eventually turned up on Find My iPhone (which I use very frequently) a month or two ago. I have to wonder if at least in a phone's case, it uses the IMEI or something in its tracking rather than merely the iCloud login since you'd expect a phone to be wiped/reset within such a long timeframe. Maybe iCloud should (or does?) do a similar thing with MAC addresses or some other sort of internal serial number when it comes to tracing lost/stolen devices.