I was working on an idea of "size of the crime multiplied by the number of people impacted" might define where the threshold lies. So murdering one person is significant in that it affects one person ultimately, and a good chunk of other people in the second order. Losing one's own phone affects a single person only, and not very significantly at that. Apple's losing their prototype is analogous in the actual act, but the effect on Apple's marketing multiplies it out big-time.
Other test cases for the thought experiment: bank robbery; simple assault; rape; creating a public nuisance. I think the idea can be applied successfully across all of these.
I don't know anything specific about the stolen iPhone case. I find the whole "zOMG I saw a picture of the new iPhone!!!1!!" thing to be ridiculous. So I can't address anyone's behavior in this instance.