NFL rules specifically state that in the event of any fumble, without possession of the ball if the ball is touched by any player who happens to be out of bounds at the time of the touch the play is over and the fumbling team will retain possession at the point of the touch while out of bounds.

So I have to ask this, if that's the rule then why didn't they blow the play dead when Gurley was out of bounds and still in contact with the fumbling ball? Seems odd to me. Player out of bounds contacts the ball and they allow the ball to be advanced forward resulting in a touchback. Missed call by the Refs in my opinion.