Once the 1st official ruled the subs in, they are in the game, should be no Tech Foul. He could send them back to the table, but probably the horn sounded & the official might not of been aware of how many shots. Subs should enter before the last free throw, however, if they are signaled in, they are in the game. No Tech & if problem, the officials should have come together.
Another thing, Coaches must not of known what had happened because that would have been a correctable error, coach could have called time out (without being charged) to get it corrected. Sounds like more than the officials, the coaches let it go.