Player fouled out...

[Nevadaref]

You are correct.
2-11-11 Note 2
The procedure if a player who has committed his/her fifth foul continues to play because the scorer has failed to notify the official is as follows: As soon as the scorer discovers the irregularity, the game horn should be sounded after, or as soon as, the ball is in control of the offending team or is dead. The disqualified player must be removed immediately. Any points which may have been scored while such player was illegally in the game are counted. If other aspects of the error are correctable, the procedure to be followed is included among the duties of the officials.

In your sitch, the officials should have used the AP to resume.

[Nevadaref]

A little more info for you.

SCORER'S SIGNAL
2.11.3 SITUATION: When may the scorer signal? RULING: If the scorer desires to call attention to a player who is illegally in the game, he/she may signal the official when the ball is in control of that player's team. If it is for a substitution, the scorer may signal when the ball next becomes dead and the clock is stopped. If it is for conferring with an official, he/she may signal when the ball is dead. If the scorer signals while the ball is live, the official should ignore the signal if a scoring play is in progress. Otherwise, the official may stop play to determine the reason for the scorer's signal.

RULE 4, SECTION 36 POINT OF INTERRUPTION
ART. 1 . . . Method of resuming play due to an official's accidental whistle, an interrupted game, as in 5-4-3, a correctable error, as in 2-10-6, a double personal, double technical or simultaneous foul, as in 4-19-8 and 4-19-10.
ART. 2 …Play shall be resumed by one of the following:
a. A throw-in to the team that was in control at a spot nearest to where the ball was located when the stoppage occurred.
b. A free throw or a throw-in when the stoppage occurred during this activity or if a team is entitled to such.
c. An alternating-possession throw-in when the point of interruption is such that neither team is in control and no goal, infraction, nor end of quarter/extra period is involved.

[Idaho]

Thanks, Nevada.