Runner touches batted ball on home plate

[tibear]

Question from another umpire site:
Bases loaded, 2 outs. Batter hits a popper out in front of home plate. Catcher charges out but ball spins past the catcher(who doesn't touch the ball)back to home plate where it comes to rest, on top of the plate, catcher in pursuit. R3 slides into home plate, touching the base, then unitentionally kicks the ball. Runners do not advanced as a result of the kicked ball.

If this happened at any other base the runner would be out because he was touched by a batted ball over fair territory but what about once the runner has already scored?

What's the call??