Illegal batting/safety

[Rock Chalk]

Here's the situation posed to me.

Receiving team A muffs a free kick inside the 5 yard line. Instead of falling upon the ball, he bats the ball out of the end zone for a touch back. The refs correctly call him for illegal batting, but where do you mark the foul from? I thought it would go under the all but one principal, marking the foul from the spot. Others thought you award the touch back and mark off half the distance from there. Others thought a safety should be called.

Thanks for the help in advance.