San Diego/Denver

[pedr]

As I said, complete amateur. I'm not even American - just interested.

What is the NFL rule on IW, then?

In any event, it strikes me as a factually incorrect term to use for what happened (and Mike Pereira didn't use it on Official Review, as far as I remember). The whistle was not inadvertant - the whistle followed and reflected the Referee's decision. The implications of that decision were a dead ball, last possessed by Denver, which logically leads to Denver retaining possession.