Could the calling official have mistakenly believed that it wasn't momentum and that the player left the court for an unauthorized reason. Isn't it a NCAA violation as soon as said player steps back on the court after leaving the court for an unauthorized reason? NFHS rules don't require said player to return, rather just to leave the court.
Then again, I know more about the final conclusions of the Mueller probe than I know about NCAA rules.
NFHS: If a player's momentum carries the player off the court, that player can be the first player to touch the ball after returning inbounds. That player must not have left the court voluntarily, and must immediately return inbounds. That player must have something in, and nothing out. It is not necessary to have both feet back inbounds. It is a violation for a player to intentionally leave the court for an unauthorized reason.