Illegal number

[WDEvol]

Had a situation in a middle school game last week where a player was in the game wearing #6. Did not notice this until we called a foul on him in the 4th quarter. In reading 3.4.3 situation B in the case book, it appears that there is no penalty until A6 enters the game as a player. However, in the interest of preventative officiating, is this something you would look for when checking the book pregame? I'm wondering if a technical foul could have been prevented if we had noticed him listed as #6 in the book before the game. (Then again, if he's listed with an illegal number after the 10:00 mark and it's then changed, it's a technical foul anyway.)

Or is this a booger not worth picking in a 7th-grade game? Just looking for input. Players wearing illegal numbers is something I've never actually seen in a scholastic game and it's never really occurred to me to check for that in the book.