Throwing team knocks the ball away following a goal.

[Nevadaref]

B1 steals the ball from A1 near the division line and dribbles down the court for an uncontested lay-in while A1 chases behind him.
A1 is unhappy that he turned the ball over and was unable to prevent B1 from scoring. As the ball drops through the net from the made goal A1 slaps it into the fourth row of the bleachers behind that basket. There are only a handful of people sitting in this area and none of them make a move to get the ball so it remains there for about four seconds.

I’m curious what people on here would do.

Some options that I’ve heard:
1. Begin the throw-in count.
2. Call a delay of game warning on Team A.
3. Call a technical foul on A1 for delaying the game.
4. Ignore it and wait until someone retrieves the ball while the clock runs then start the throw-in count.
5. Whistle to stop the clock. Have the ball collected and then administer a throw-in to Team A.