By rule, if there is an inadvertent whistle while the ball is loose from a fumble, the fumbling team may choose to take the ball at the spot where possession was lost, and have the down count, or replay the down at the previous spot. There is no “clear recovery” rule in high school.
And it goes without saying that an official on one sideline has no business blowing the whistle on a play that’s on the other sideline.