Trade secret and top secret are two very different things.

In any case, while it is possible that the loss of such a prototype could have devastating implications for a company, it seems pretty clear that this publication was not a serious problem for Apple.

Why, exactly, is it "clear" to you that this publication isn't an ongoing serious problem for Apple? As you can tell, I'm a bit baffled by how blase people are about what's happened here. Just because it happened on the Internet, and the sky didn't immediately erupt with lightning and fireballs, doesn't mean that something momentously bad didn't happen.

I think the reason people are blase is because the story makes it seem like Apple brought the problem on themselves. The leak was utterly mundane; no one broke into the Apple campus or smuggled anything out, no one bribed or attacked an employee. As far as we can tell from the story, Apple regularly dresses up its research prototypes and takes them for walks outside. This practice is so obviously prone to leaks that people are speculating that Apple leaked the phone on purpose.

Either Apple had calculated the risk and found it to be acceptable, or they never planned against the possibility of losing the phone. If the former, then Apple is merely experiencing an inevitable downside of its chosen (wildly successful) development model. If the latter, then Apple was foolishly optimistic and should never have let a readily identifiable prototype off-campus in the first place.

I know this assertion about trade secrets not to be true. Things that are more valuable than research prototypes go for walks outside all the time. Maybe it's that context, which I get from my field of work, that's lighting me up so much.

I think you're dead flat-out wrong about this, but I understand where you're coming from.

[update: the San Jose Business Journal is reporting that Apple outside counsel reported the phone stolen. So much for the "it was a publicity stunt" story.]