Muff during Spot Throw In?

[Nevadaref]

Originally Posted by bob jenkins

I agree.

But, there is (or was) an NCAA case play to the effect mentioned in the OP (after "controlling" (and I don't mean to imply Player Control) the ball, and then losing it, the player may retrieve it, return to the original spot and complete the throw-in)

That's correct. Here is the ruling from the NCAA's 2008 Case Book.

Throw-in

A.R. 157.

A1, on a throw-in from a designated spot, fumbles. A1 leaves the
designated spot to retrieve the fumble. Is this a violation?

RULING: No. Since there was a fumble, the official shall blow his/her
whistle, which causes the ball to become dead, and then shall re-administer
the throw-in.
(Rule 7-6.5)

The NFHS has such a ruling for a FT shooter, but not for an inbounder.
FREE-THROWER LOSES BALL
9.1.1 SITUATION: A1, at the free throw line to attempt a free throw (a) muffs the pass from the official and it rolls forward; or (b) accidentally drops the ball before the throwing motion is started. RULING: In (a) and (b) the official should sound the whistle to prevent any violations and then start the free throw procedure again.