This might, might be a prototype: they do tend to be bigger and uglier than the device as released. But some aspects just seem wrong and un-Apple like: the volume control buttons (ugly, unable to discern which is up or down just by touch) and the huge bezel. Overall: it’s either a fake or an early DBT unit.
If you read the links provided within this link to Gizmodo and Engadget, it’s fairly convincing that this is actually the device. 1) Apple admitted to missing the device and wanting it back. 2) Apple remotely killed the phone, and 3) the phone was pictured next to a prototype of the iPad in an Apple-released photo. Also, all parts inside are Apple.
Device is a legit Apple next-gen iPhone prototype. It was issued to Gray Powell an Apple Software Engineer working on the iPhone Baseband Software (the program which enables the iPhone to make calls). He was celebrating his birthday at Gourmet Haus Staudt in Redwood City and, ah, somehow left his next-gen iPhone he was testing on the field (disguised as an iPhone 3GS) on the floor of the beer hall. Gizmodo bought it from the guy who found it. Apple’s in house counsel has now sent Gizmodo a letter asking for it back (posted on their site).