The act of him not doing enough to return the device and then selling it makes it theft. Not that he found the iPhone, the fact that he didn't do much really to return it and then sells it makes it theft.
Problem with that. Apple employee has no means of getting it back. Founder did not leave it with the bar management or did not tell bar management. Founder did not turn it into the police station. Founder called CS department who would have no idea what to do. Founder then sold device to Giz. Apple Employee did not know the person who found it. So how was the Apple Employee supposed to go back and get it back again?
good point, if you found someone's phone or wallet at a bar, why would you want to bother with it. Wouldn't the first normally honest impulse be to turn it over to the bar management for their lost and found? It can't be the first thing of value someone has left accidentally at that bar.
Forget that it's a iphone prototype, just say it is someone's run of the mill phone. Why would you take it from the bar where it is likely they would come back looking for it?