Water Cooler Play - Actionless Contest?

[HawkeyeCubP]

NFHS rules.

Team B only has 4 players - B5 is not there yet, but is "almost there," on their way. Opening jump ball is tipped OB by B jumper. Team A, being told the game will re-start regardless, does not want to continue until the 5th player is there. A has the throw-in, and reaches across the boundary plane, drops the ball onto the playing court, and leaves it there. Neither team moves to get the ball.

What do you do?