Muff during Spot Throw In?

[Freddy]

Gals and Gents,

Sitch:
"The thrower on a spot throw-in with the ball put at his disposal, after muffing the ball which rolls away from his spot out-of-bounds, may go retrieve the ball, return to his designated spot, and throw the ball in without a violation."

This was expressed to me by a credible source. As with anything I hear, I want to run it by the rules, and I can't find anywhere that this is allowable. Only that, "The thrower must keep one foot on or over the spot until the ball is released." (4-42-6 NOTE).

Has anybody ever heard of such a thing not being a violation?