On my initial run for the Dead Messenger this week. I completed the event (boss kill), and the fireteam leader booted me from the session prior to reaching the terminal in Vox Obscura on Legend.
I have done runs later this week, and I have unlocked additional parts for this pattern. However, the Dead Messenger pattern still has not dropped.
I am concerned that the game is counting my boss kills, but the game still won’t make the pattern available to me for crafting.
Dead Messenger Pattern Lock