Infield fly situation

[rbmartin]

OBR rules. Bases loaded, no outs, right handed batter at plate.
Batter hits a high pop-up which could be caught by the pitcher "with ordinary effort". The umpire immediately declares "Infield Fly, Batters out if Fair!" The pitcher, upon hearing the umpire, allows the ball to fall to the ground in fair territory about half way between HP and 1B. No other fielders make an attempt on the ball. The runners, knowing this is potentially a live ball begin to advance to next base. Due to the spin on the ball, the ball abruptly skips sideways and is obviously headed to foul territory when it hits the Batter/runner in fair territory (out of the box and in route to 1B). Ball is inadvertently kicked into the dugout by the B/R (this action is in no way intentional).

How do you sort out this mess?