NFHS Illegal Sub / Umpire Screwup

[SRW]

Thought I'd run this by thr group for an opinion. This was presented to me today, and I had mixed feelings.

NFHS Varsity Game between Team A and Team B.

Team B's pitcher was a runner at second base. Team B coach asked the plate umpire if he could use the same courtesy runner that had run for the catcher earlier in the game. The umpire said he could. After a pitch to the next batter Team A's coach protested that the courtesy runner was an illegal substitute. After much discussion the umpire ruled that the courtesy runner was illegal and restricted her to the bench for the remainder of the game.

What is your opinion of that ruling?