a77,
You handled it fine. It sounds as if the coach was trying to teach his team to be responsible and communicate with each other when they substitute. You allowed him the opportunity to do that with his team. I have no problem with how you handled this.
Furthermore, since you were aware of the situation and didn't put the ball into play, there is no technical foul to call. There were never six team members participating. They were simply slow to leave the floor during a dead ball.
Nice game awareness.
