Ref kills live ball on inadvertent horn - sub?

[Nevadaref]

For NFHS the rule is simple and clear. If the clock is stopped and the ball is dead, then a properly reported or reporting substitute shall be allowed into the game, barring the restrictions for multiple throw FTs and previously exiting players when the clock has not yet run.

Preventing a legal substitution in an NFHS contest is just making up your own rules. Quality officials don't do that.