Scorer's Horn During Live-Ball

[CDurham]

Had this play last week in summer league.

A1 is starting his drive around the 3 point line and right before going up for a lay up in the post the scorer's horn is heard. A1 hearing the horn stops and throws the ball in the direction of the lead official who in turns lets the ball go out of bounds. The lead signals Team B ball going the other direction.
A1 makes the argument that he heard the horn and thought that stopped play
The lead argues that even though the horn was sounded it was during a live ball which therefore should be ignored if a scoring play is in action.

I didn't over rule the call because it wasn't detrimental to the game (Team A down 20 in the 4th quarter) and wasn't asked by my partner. However me and my partner did discuss the play after the game. My thoughts are yes it was during a live ball and during a scoring play, but I view the case of ignoring the signal only when the scoring play continues after the sounding of the horn. If a player hears the horn and throws the ball to the official it obviously caused a disadvantage towards A1.

In others words I think this play and the case play in the book 2.11.3 is stating that if the horn is heard during a scoring play it should be ignored if the scoring play continues. If it does not like in the play last week play shall resume from the point of interruption.

Would like to hear everyones thoughts! Thanks