So EVERYONE deployed on the particular ship that supposedly shot that missile has been persuaded to keep quiet??
Why do you think that would be hard? The military is not a democracy. It kills people.
that is exactly the flaw with all conspiracy theories. No one can keep a secret! Ever.
I am not sure that it was friendly fire, but let's answer your question.
While everyone on one ship might be aware a missile was fired, how many missiles did that ship fire that day ? How many ships were firing missiles ? (this was a military exercise including ships from many countries).
How many men 'on the ship' were standing around on deck watching the sky ?
Have you considered the alternative ? That it wasn't a 'missile', per se, but one of the drones the missiles were to be aimed at ?