Player enters a court without being beckoned.

[Sharpshooternes]

Sophmore boys game today, I was standing at midcourt ready to hand the ball to the thrower-in-er. I hand it too him and he passes the ball to A2 on the court. Horn sounds and B6 walks on to the court to sub for B1. I blow the play dead and tell B6 to get off the court and make him wait. Until the next opportunity to sub. I don't think I handled the situation by rule but no one complained and my varsity official said I did it correctly. I was just going to ignore the horn because I knew it was for a sub, but the player walked on to the court.

I think by rule it should have been a technical foul charged to someone (team, player? I don't know.) Some advice on the proper way to handle this in the future would be appreciated.