Ball bouncing away after made basket

[zebraman]

Boys 4A Varsity. Team A scores a field goal. After going through the hoop, ball had some "backwards spin" on it and starts rolling downcourt. B1 and B2 are ready to throw it in along the endline, but the ball is at the free throw line and rolling... now at the top of the key and rolling towards half court - clock running of course. No pressure from Team A so the ball isn't going to be picked up by anyone.

Blow whistle? Common sense or is there a case book play to back it up?

Thanks,

Z