Illegal Forward Pass Question

[Altor]

This was the sequence in the video.

1st and 10 from A20 with 0:18 (according to the announceers). Completed pass to A27, followed by an incomplete pass that lands at the A32. L initially drops his bean bag, but after blowing the play dead, marks the ball at the A27 and decides he should have thrown a flag instead.

After an initial discussion, R signals an illegal forward pass, says it was declined and gives the ball to team B. After further discussion, he signals the illegal forward pass, says the pass was incomplete (which looks like it's being declined), loss of down, 2nd down. While he's explaining, U is marching off 5 yards. Result of the play is ball on A22, 2nd and 8, 0:06 remaining.