Once the article went up there wasn't much they could do. Sure they could send a cease and desist, or file a lawsuit, or any other number of things...but the reality is that once it was out there, there was no putting the cat back in the bag. All they'd really accomplish by suing Gizmodo, Engadget, and the other tech blogs is that they'd come off looking bad to all the people that follow the blogs.

Instead of bitch slapping the reporters, they can just punish whoever lost the phone, and read the comments and reviews about the prototype to get some valuable early feedback about their device (especially since they still have a bit of time to make changes to the design/software/features if need be). Most of the public will never bother going to these blogs anyways, so the vast majority of people won't see it until it's announced and advertised. If they leave it alone they keep a very important part of their customer base happy. (all this is assuming it was a mistake that the phone got out....if it was on purpose, then of course they don't care )