Need a Rule Interpretation

[Blu_IN]

NCAA Rules. Runner on third.

Batter-runner hits a ground ball to F6. F6 throws to first. The throw is low and F3 cannot hold onto the ball and the ball rolls away. Clearly a safe and I do not signal anything. The batter-runner believes that F3 caught the ball and thinks she is out. She heads for the 3rd base dugout and is approximately half way between home plate and 1st base. The defense realizes the batter-runner is off the base, grabs the ball and tags her.

I ruled this as an out and would like to hear what you all think about this situation. I ruled that batter-runner had liability to be put out in this case. The rule that allows a batter-runner to run through first did not apply to this particular situation. This was a mistake made by the offensive player.