Well, I'm not sure if it helps, but in every rule book I've used for playing or refing, it doesn't matter where the hell the ball is.(indoor, outdoor, club, high school, collegiate, fifa) The keeper can grab it from anywhere, as long as while he is touching it no part of his body is on/over the white line. The keeper can reach across the line and grab the ball, he just can't step over it with the ball.
For better or worse, however, this almost never comes into play. The ball moves quickly enough in indoor that if the keeper is that far out while an opponent has the ball he's screwed anyway. If it's rolling toward him from a teammate, it doesn't matter as you can wait an extra half second. If you are in that big a hurry use your damn feet.