Pavonis Interactive Forums

There were 2 dark events preparing. One that gives armor and another hidden. I received a guerrilla mission with "Counter hidden dark event" reward. I did it with success and flawless status but didn't receive any popup telling me dark event was stopped, the two dar events listed before still remain on the list and finally were trigered.

What I missed?

You didn't miss anything, the system is frustrating in not telling you which dark event was countered.

It's also possible for dark events to prepare in regions you have not yet contacted.

I'm pretty sure the mission blurb tells you which Dark Event it counters.

Perhaps in this case it was an undiscovered DE that was shut down?

I don't think you can have "undiscovered" dark events (DE not listed in the list of "preparing" DE), just Hidden ones. Maybe there was a bug (there's a bug where a DE can complete while you are infiltrating the mission to counter it) or a new hidden DE just started after you countered the previous one. Advent activity goes on continuously in LW2 so Dark Events are not created at the start of a new "month".
When you counter a hidden event, you know you countered something but you don't know what. You'd have to pay the 5 Intel to reveal it to know but i find this feature useless. If you don't see the mission you can't counter it so it doesn't really help to know what will happen and if you get the mission, it's always useful to stop a DE no matter what it is so ...

Did the hidden event activate shortly after the mission or after a long time?