Little help please: Previous Spot or Not

[dannyboy]

4th and 3...QB in shotgun, defender chases until he finally catchs, using the facemask/helmet opening drops the QB. Flag. (Ok easy enough right)

Official signals facemask, Turns ball over to the defense. Declares to sidelines that it is not automatic first down. Signals first down on turnover to defense. Sideline questions the call, Officials sternly indicates it is not an automatic first down!- Never asks any of us, that isnt the point.

Arent live ball fouls on runs assessed from the spot? Does anyone have a great way to memorize basic, previous etc spots on enforcement of penalties?

Thanks