https://support.ubisoft.com/en-GB/
This is just the general support for Ubisoft. That I googled and copied and pasted here.
You can also DM one of the mods and they should be able to help you with it as well.
You can also get the that particular reward in the game now. By defeating the boss named “coyote” she is located in the Jefferson trade center. Playing in a group will better your odds especially if the group is willing to drop it for you if they get it and you don’t. Group of 4 being your best chances of course. Though personally I played that mission several times one day and it never dropped but I was playing on challenging and for best odds you need to play heroic.
Also it SHOULD have a chance to drop from any mission that has face mask as targeted loot. Exotics can drop from just about anyone in a targeted loot mission. I just had the exotic BTSU glove drop from a purple enemy.
Hope this helps