Illegal Sub? - or nothing?

[waltjp]

NFHS Rule 3-7-3
During the same dead-ball interval, no substitute shall become a player and then withdraw and no player shall withdraw and re-enter as a substitute unless a penalty is accepted, a dead-ball foul occurs, there is a charged time-out or the period ends.

Case Book 3.7.3 Situation A
B11 mistakenly believes he is his team's 12th player and leaves the field before the snap (b) on his sideline and enters his team box. B11 then discovers his error and returns to the field on his team's side of the neutral zone before the snap. RULING: In (b) once he left the field, he was no longer a player, and by coming back onto the field, is an illegal substitute.

Redding Page 127
A player who returns to his team box, realized he was supposed to stay in the game, and then returns to the field does not commit a foul because he does not lose his status as a player when he enters the team area while the ball is dead. He is not a replaced player because he was not notified by a substitute that he was to leave the field and he is not a substitute because there was not a player vacancy for him to fill.

The NFHS Case Book has an * indicating this as a change. Last year's Case Book said this was legal.

Redding also has their play highlighted as a change for this year.

So, foul or no foul?