Your analogy breaks down a bit because you can't really lose a car the same way.

Naturally not, but one might easily lose the keys, and I read your example of the car as a proxy for the phone prototype.

I see where you are going with the bar example, but I'm not sure I get your point. Presumably in the case of the Facebook identity the finder of the phone remembered it at least well enough to assist Gizmodo with finding the Apple employee. And obviously it did not get handed into police or anyone else, (like the bar or an Apple store).

Anyway, rather than arguing by increments I'll cut to the chase: if I were actually a lawyer seeking to take action against Gizmodo, I'd be basically arguing a claim of misappropriation under section 3426.1.(b).2.C of the California civil Code (which is basically the Uniform Trade Secrets Act), as follows (heavily edited for clarity):

"... (b) Misappropriation" means: ... (2) Disclosure or use of a trade secret of another without express or implied consent by a person who: ... (C) Before a material change of his or her position, knew or had reason to know that it was a trade secret and that knowledge of it had been acquired by accident or mistake.

In plain English, we might dismiss the guy in the bar as a tipsy opportunist who was told there was a reward on offer (and who had no especial duty to guard Apple's secrets, vs. a duty to hand in lost property in general). However, Gizmodo had reason to know an iPhone prototype would be a secret thing: they published entire articles demonstrating their knowledge of Apple's secretive policies, as well as recent C&D letters from Apple's outside counsel asking Gawker to stop offering money for secret information. As I said before, they may not have known for sure if this device was a real Apple prototype, but they surely hoped that it was - it wouldn't have had news value if it wasn't. If it had just been a first-gen iPhone, there'd be no story. They materially changed their position by exchanging money for it. And they knew it had fallen into the hands of the seller by accident (at best).

If the fellow who sold the phone had instead taken pictures and set up weird_found_iphone.com, he could plead ignorance about the significance of his find. But it seems very hard to me for Gizmodo to claim the same thing. $5000 says they perceived the thing to have major newsworthiness. The prototype didn't cease to be secret just by virtue of its being lost and found; were that the case, then it wouldn't have been worth paying for. On a side note, there have been successful prosecutions for sale of trade information by a waiter employed to help cater a boardroom dinner; the careless sharing of company information to this non-employee's benefit didn't lessen the information's secret nature.

So Gizmodo purchased the device with the specific intention of exploiting its secret nature. The employee who was (we assume) field-testing it was meant to keep it secret, and did so by leaving it in its plastic disguise as an iPhone v3. He failed to keep it securely on his person as he should have: but whether careless, drunk, or both, this was surely a mistake. It's not as if he handed it to someone saying they should check it out, and then wandered off and never retrieved it. Nor did he disclaim ownership by throwing it in a garbage can or something. Loss is involuntary by its very nature; the guy called the bar repeatedly in hopes of finding it (as any reasonable person would expect). And while the finder might not have appreciated just how Apple would feel about their prototype, Gizmodo could hardly have been more aware, being in receipt of formal warnings from the company.

So my argument is that they distributed and used the info (as news to attract traffic and sell ads); they did so knowing it belonged to Apple; and knowing that Apple would not be happy; and knowing it was a prototype of an unreleased product; and knowing that it had come into the seller's possession by accident; and handing over a large sum of money because they understood the huge potential benefits of gaining this specific information.

Don't even get me started on the legalities of dissecting, photographing, and publicizing the innards of the thing.