Freshman game yesterday. 3rd and 7 for A on the A 43. A's QB takes the snap, turns to his right and fires a backward pass to a back who is split out about 5 yards. The ball is muffed by the back and recovered by B30 at the A37. After the muff and while the ball was loose on the ground, an inadvertent whistle sounds.
What do you have? (NFHS rules)

Why the whistle in the first place? Talk with the official who made the call. Did he feel it was an incomplete pass? If so, A's ball 4th and 7. If it was an inadvertent whistle, it is A's ball. Replay the down or they could take the result of the play. Unfortunate but a mistake was made by the officials. Let the coaches know you made the mistake a must follow the inadvertent whistle rules. A win win for the offense.

If the ball is loose following a backward pass the team last in possession may choose to put the ball in play where possession was lost or replay the down.

Only the team that was in possession proir to loose ball has a choice. They will want to replay the down.