Batter Interference

[Umpire47]

I am confused. (Runner on 2nd.)The ball gets away from the catcher, and the runner takes off to third. The ball rolls right near the batter's foot, he inadvertantly steps on the ball while in the batter's box, while the catcher is reaching to grab it. The ball rolls off, disallowing the catcher the chance to pick the ball up and throw to third. Is this Batter's Interference? Please give some basic rules of thumb for this rule.