Free Kick question.

[bigjohn]

ART. 1 . . . It is a touchback if any free kick or scrimmage kick:
a. Which is not a scoring attempt or which is a grounded three-point fieldgoal
attempt, breaks the plane of R’s goal line, unless R chooses a spot of
first touching by K.

If K muffed it, they did not recover it or possess the ball. Kick doesn't end unless possessed. R has options but will take the touchback.