Whistle in or out during free throws?

[fiasco]

Usually I have my whistle in my mouth at all times during the free throw, with the exception of when I'm L administering, I spit the whistle out right as the ball reaches the rim, just in case it caroms off the rim and hits me in the mouth (yes, it's happened).

I'm starting to rethink this practice after last night. I'm T on free throws. Just before my partner is about to administer the ball on the second of two free throws, I hear some commotion behind me at the bench. I turn to look and see a sub at the table wanting to come in before the free throw. By pure instinct, I start to put air in my whistle. Not a full blast of air, because I'm thinking to myself that my partner has probably already administered the free throw, but my instinct to blow got the best of me and I put enough air in my whistle for everyone to hear. The scorer hears my whistle and blows the horn to signal the substitute.

As I turn my head I see the free thrower has the ball. Groan.....

I motion for the sub to stay at the table and nod at the free thrower to proceed. His coach is standing behind me a little upset that I've blown my whistle and "distracted" his player right before he's to shoot.

Trying to think how to avoid this in the future.

First, I should have turned to check and see if the shooter had the ball before putting air in my whistle. I'm just thinking maybe if I had the whistle out of my mouth at that time, that would have given me enough pause to be able to catch myself before the shooter had the ball. Also, should my partner have re-administered the free throw?

Where is your whistle during the free throw? I'd like to start the habit of waiting to put it in my mouth until just before the shooter releases the ball.

Thoughts?