Here's a good what-if...
If R HAD come down with the ball in possession, then illegally tossed it forward, it would be an illegal forward pass after change of possession. They could decline the hold and keep the ball... except that the foul occurs in the end zone (behind the basic spot of the 20, since it was A's force into the endzone) -- and resulting in a safety. (So, they won't decline the hold, obviously, resulting in a double foul, replay the down)
Hypothetical part B -- what if A doesn't commit the holding foul.
Now, how long will it take to convince A's coach that they didn't recover the incomplete pass for a TD?