After looking at it again, I don't think he realized that he was out on the field. He must have thought that it was a loose ball which had already crossed the sideline. Of course, that doesn't say much for their sideline discipline, having already had one warning...
Check it out again...he made a intentional grounding signal before or while he bent down to get the ball. He thought it was a dead ball. Which still doesnt matter, a backwards pass/fumble is still live if you intentional ground it or not. He of course said he didnt touch it and I havent really seen one replay where it shows conclusively that he did.WDMS