Don't mix apples and oranges. Do officials miss fouls. Yes. But the OP says the HC followed proper procedure. He called a TO to discuss the misapplication of a rule.
Rule 3-5-11 states that:" . . . A player, directed by his coach or the head coach, may request and be granted a time-out for the purpose of the coach and the referee reviewing a decision which may have resulted from misapplication or misinterpretation of a rule, provided the request is made prior to the time the ball becomes live following the play to be reviewed, unless the period has officially ended..."
The case book gives the following guidance:
3.5.11 SITUATION B: Following a fourth-down incomplete forward pass late in the fourth period, a time-out is properly requested for a coach-referee conference regarding possible misapplication of a rule.
(a) The coach of B questions a pass interference call on B1 during a second forward pass by A1; or
(b) the coach of A questions why no pass interference by the defense was called and why the covering official inappropriately signaled that the pass was not catchable.
In either case the referee determines the coach was correct and an incorrect ruling and inappropriate signal had been applied.
RULING: In (a), the penalty marker is picked up. In (b), a penalty marker may be dropped and the pass interference penalized. Misapplication of a rule or an incorrect signal may result in picking up a flag or dropping a marker to indicate a foul did occur and gives the appropriate signal.
So, Yes, you are going to admit that a rule violation has occurred and you are going to fix it, not ignore it. The rule which fits is the nonplayer USC foul that is enforced from the succeeding spot.