Where are you seeing this? The only place in the rule book I see the coach losing the box for reasons other than a technical foul is this from 10.5.1 Sit A:

RULING: Legal. The coach is not required to use the optional coaching box even though it has been adopted by the state association. However, if the coach begins the game by sitting somewhere other than where the box is located, he/she may not use the box privileges any time during the game. The coach must begin the game in a position within the box if he/she wishes to stand when *permitted under the optional coaching-box provisions.

It is even funnier the questions that Iowa coaches ask when I have worked games when they come to Illinois.

I was even in a game some years ago where the coach got ejected for not sitting down after getting a T. Then he claimed he was not told (by even the opposing coach) that he could not stand or the rules differences with the coaching box.

Funny thing this was just a coach that was a former coach of the team he was playing (won a state title too with that school) and was just across the Mississippi from the host school as well. The fall out to that incident was funny.

Peace

"Beware of the Beginnings"
 

"...if the coach begins the game by sitting somewhere other than where the box is located, he/she may not use the box privileges any time during the game. The coach must begin the game in a position within the box is he/she wishes to stand when permitted under the optional coaching-box provisions." (10-5-1C)
However, schools do us no favor when they set the chairs up so the innermost and/or the outermost chairs are outside the coach's box. The coach naturally wants to range from or sit in the innermost and outermost chair and go from there though that is way out of the box.
We had one official in the area who would move the chairs to reflect this situation. He made several AD's livid. If anything he shoulda mentioned it to the AD and let him take care of it.
GV the other night I asked the coach to start out in the coaching box and he acted as if I was an alien from the planet Murdook. He said, "You mean I have to stay in this area?" I said, "Yes." And he did--the entire game. He was either testing me at the start to see if he could boss me around, or he had never heard of the rule governing the box before. I think the former, not the latter.
Easy for U1 to tactfully set the expectations just before the jump ball. Just wish all U1's would do it early in the season so we don't have to keep instructing coaches the entire year. Laziness or indifference on the part of some makes it harder on the rest.

In AAU games, I will move the chairs myself. For HS games I will tell the teams we need to move those chairs away from the table.

10.5.1 A indicates a technical foul is to be issued there as well (unless they changed that this year...I looked it up in last year's book).

I think I was incorrectly taking the ruling that if a coach sits outside the box to start the game, he/she can't use it for the entire game and transforming it into the idea that if a coach leaves the box and sits on the bench outside of the box for any reason he/she loses the coaching box. Q#9 in the OP got me to thinking about this, but in reading the OP again, the answer provided didn't dictate the coaching box be lost. So I went back and reviewed the rules and the previous posts again. I guess my issue is that I've never thought of the coaching box like a prison that can't be left and I guess some of that stems from the fact that it isn't enforced like a maximum security facility. I don't think this whole discussion really change anything, but it does give me a better understanding of the rule.

...and even by official.

...unless you are in Iowa, in which case if you start in the coaching box, and then go sit down somewhere outside the coaching box, you have essentially forfeited your coaching box privileges for the remainder of the game.

That would only be due to being charged with a technical foul for leaving the coaching box. It can't arbitrarily just be taken away.

Not according to the original post. Go back and look at question 9 again. There is no mention of a technical foul.

There is also no mention of him losing the coaching box or forfeiting it as you wrote. The Iowa question and answer mere states that what the coach has done is not permissible. When a coach does something which isn't permissible, the only penalty that I know of is a technical foul.

I can see warning the coach for being outside of the box, but we don't take it away without issuing a technical foul.

OK, I can buy that.