The headline kind of says it all. Go to MLB.com for the video and the full explanation.
To answer your immediate question, a fan grabbing a ball is not an automatic double. It’s often treated like that, but it’s an umpire’s judgement call as to what would have happened absent the interference, and I think the umps got this right.
People: they’re baseballs. You can buy one for, like, four bucks. If you try hard enough you can even get Dustin Ackley or whoever to autograph it for you when he appears at the Home Depot or something.