Only Steve Jobs and Jonathan Ive know how the final product will look like.
I'd be very surprised if Steve would give the actual iPhone 4G to a 27 year old engineer who got drunk sometime in March and forgot about his phone
What the engineer probably got was the technology of an iPhone 4G, not the actual hardware! It looks like they stripped the phone off his (ergonomic) shell. That would explain the nakedness of the prototype.
It's amazing that the internal hardware fit perfectly inside this shell considering that it was actually designed for another more ergonomic shell. /s