Flagrant foul for number change?
 

This seems like an excessive penalty for not reporting a number change to the scorer and an official. I can see a player who had blood on a uniform changing uniforms and neglect to inform anyone after the change, most likely from ignorance from the rule not in effort to deceive the officials. Not that I am excusing ignorance but has anyone had any experience with enforcing this rule and how did you handle the coach who went ape s@!# crazy when his leading scorer gets tossed for this?

It also states that they must inform the scorer AND the official. How does this procedure usually work? Dead ball, when they sub in, at the time of the change?

Usually when it happens. The coach usually tells the official who tells the score and the opposing coach.

I've never seen it not be reported.

Ignorantia Juris Non Excusat ...
 

"Ignorance of the law excuses no man: Not that all men know the law, but because 'tis an excuse every man will plead, and no man can tell how to refute him." (John Selden, English Jurist (1584 - 1654))

My guess is the punishment is so harsh because someone years ago probably decided to try to hide their best player – and his/her four fouls – by changing that player’s number at halftime without telling anyone.

As for blood on the uniform I had it happen two seasons ago. The coach asked me what he could do to get the player back in the game and I told him (the kid took the jersey from a teammate who wasn’t going to play). I also told the coach both players had to make the uniform exchange away from the visual confines of the court. :)