Under CA law, the finder of a lost item, if they can reasonably find the owner of the lost item, is required to make "reasonable and just" efforts to return the lost item to the owner.

The claim by Gizmodo (and presumably the finder) is that the finder called the Apple customer service line and didn't get anything useful, thereby fulfilling the requirement.

The claim by those who say this was theft under CA law is that this did not fulfill the requirement, since it was found in a bar, and it is extremely reasonable to contact the bartender about a lost item that was found in the bar.

If you concede—for argument's sake—the group claiming theft is correct under CA law, and Gizmodo knew the backstory—which they presumably did—then they purchased stolen goods.

One of the people at Gizmodo (Nick Denton? memory fails right now) even admitted it was stolen when offering to return it to Apple, although the page containing the admission has since been edited.