Scenario:
Player A casts an instant and passes priority. He has one untapped land.
Player B casts Flusterstorm targeting the instant.
Player A asks player B if he passes priority. The answer is yes.
REL is competetive.

My question:
Did Player B miss the storm trigger with the effect that Player A can use his last mana to pay for Flusterstorm?
At least Player B didn't announce the storm trigger and therefore he didn't choose a target with copy.
On the other hand I have found this:

Triggered abilities that do nothing except create one or more copies of a spell or ability (such as storm or cipher) automatically resolve, but awareness of the resulting objects must be demonstrated using the same requirements as described above (even though the objects may not be triggered abilities).

For example, the Storm ability of Empty the Warrens is not considered missed even if the spell’s controller does not specifically announce the trigger before passing priority after casting the spell. However, if that player then forgets to put the additional Goblins onto the battlefield before moving on with his or her turn, the Storm trigger would be considered missed after all. Again, this is a concession to the way players actually play magic.