Nobody I've talked to seems to think that this scenario is okay or would consider the laptop "lost".
I'll tell you: I would feel nothing, because I would never ever find out.
If, say, this guy had conspired to break into Apple and steal this thing or stalked the engineer and thieved it outright, then there is a difference. I don't know and don't care if there isn't one by law, it's just not the same.
I think this guy made a bone head decision. I think Gawker did too. I also think mistakes happen and that punishment should fit the crime. What do we know about this crime and the damage it did? It's hard to gauge, but I don't think it's so criminal that people belong in prison for it. This wasn't the nuclear launch codes.
He belongs in prison if he is found guilty on the broader principle of justice. I am referring to the principle that says that a man that robs you as a private citizen should get at least as severe a penalty as someone that robs a large group of people (in this case, Apple's employees and shareholders). This is required if we are to maintain our rule of law and the benefits that it entails.
His theft resulted in Apple's loss of millions of dollars in trade secrets and marketing. That's one claim that would require a mountain of proof. Until then, prototype or not, its a $400 phone.
When Apple almost went bankrupt in 1997, they were one really leaky ship. Everyone knew what they were working on, so when Macworld time came around, there were no real surprises. Steve Jobs realized that they were losing millions in publicity by screwing this up, and he stopped the leaks and saved Apple. Obviously he did a lot of other things that had a lot to do with their success, but stopping the leaks did have a very measurable impact on them.
Edit: I forgot to mention this earlier, but the Osborne effect is probably the larger factor to consider here. Lots of people will be waiting to get new iPhones now (myself included).
Of course, using reality-based logic, the story is a little different. The reality is that if this incident caused Apple to reschedule the iPhone unveiling by one day, or pushed the release date of the phone back by a week, or took an engineering team offline for a couple days, or forced Apple to spend 80 billable hours with outside counsel, or... look, there's probably not a single action Apple could have taken in response to this that doesn't immediately incur 5-6 figure damages.
Could this guy have possibly realized that? Not Apple's problem. Not the world's greatest caper, this one.