Whistle required?

[bucky]

During a throw-in, the ball is passed across the court and goes out of bounds, touching no player. Because of the violation, the opponent now has a throw-in at the original spot.

We know this play/rule.

Does anyone know of any documentation (manual, mechanics document, etc.) that requires an official to blow their whistle when the throw-in pass goes out of bounds without touching anyone? Would love to see it if you do.