IP with F6 in Foul territory prior to the pitch

[Rattlehead]

14U Tight Game. 1 out and R1 on 2nd. ASA Rules

Defense is in tight to cover the bunt. F3 and F6 moved up prior to the pitch.

Pitcher releases the ball and the batter bunts up the third base line.
Batter-runner takes off toward 1st as I follow the ball F6 (Who hasn't moved since before the pitch) sets up to field a fast moving bunt up the third base line. She is straddling the third base line with her right foot about 12 inches outside the line.


After looking this up I should have called an Illegal pitch, but not being sure about the penalty I kept my mouth shut.

How would you have handled this in a normal situation if you had not spotted the field positioning till after the batter has made contact with the ball and you are positive that the fielder had not moved into foul territory after the pitch had been delivered?