That's not good enough, in a court of law. Like many other people on here have said... It's like buying a Rolex (or TV, whatever) from a guy in a back alley. He might have SAID that it wasn't stolen, but you have a reasonable expectation, according to the law, to believe that he's lying. It's GIZMODO'S RESPONSIBILITY TO DETERMINE THE VALIDITY OF THE SELLER... BY LAW!
this.
...and the $5000 price tag for a phone, shows they knew (and hoped) it was likely an Apple prototype that wasn't sold to the public yet, i.e. Apple's property.