IW on try (NCAA)

[ZMan]

This weekend I was at a college game and the crew had an IW after a kick try was blocked. What is the proper enforcement in the following scenarios?

A) IW occurs before B recovers the ball.
B) IW occurs while B has recovered the ball and is running towards A's end zone.

The whistle was blown before B recovered the ball and the crew basically ignored the whistle and A kicked off. The try was not replayed.

Thanks.