Substitution Question?

[Indy_Ref]

End of 3rd quarter, after the buzzer...A1 gets a technical foul for taunting. We start the 4th quarter with B shooting 2 FT's & getting the ball OOB at halfcourt. (Of course, the arrow is pointing to B...so we make sure that the bench does NOT change the arrow after B completes the throw-in since B is getting the ball because of the technical foul and not because of the arrow.) While I am administering the 2 FT's, a substitute reports for A1. He was NOT there at the 15-second buzzer to start the 4th quarter. Before I could say anything, partner brings A6 in for A1. Although I don't agree, I let it go so as not to show him up...or to embarrass myself in case he CAN come in legally. Plus, it was a 20-point blowout...so no one really cared.

Question: Can A6 enter in this situation? I say "NO" because he was not there by the 15-second buzzer to start the quarter...and a sub, who has not reported in time, cannot enter unless time has come off the clock or unless team A calls a timeout. I have looked over the substitution rule and still believe that A6 cannot come in.

Please advise!