If you "should have" called illegal batting, then A has two options: they can accept the result of the play, touchback, 1/10 @ A20, clock on the snap.
Or (more likely) they can accept the penalty for illegal batting, 15 yards from the previous spot (basic spot for a loose ball play), which would give A 1/10 @ A32, clock on the snap.
I agree with TampaSteve: this illegal bat needs to be obvious to get a flag. And it also needs to be clearly the force that caused the ball to go over the GL to get a TB.