Ok, here's what worked for me. Do the assigned mission the sword has regardless of which one it is. Like others have said it will eventually give you the psionic one you need. That's step 1. Now, once you get on the Psionic mission you must remember a very important part that the mission notes do a piss poor job of telling you.... At the very end you have a node you must protect. You CANNOT allow ANY of the psions to turn into flayers. If you allow even one to convert you have failed the mission. I completed the mission and did not get any progress. Thought what the hell. I know I just did it. Went back and researched a bit and noticed the requirement about the flayers. Did the mission again making sure to pay extra attention and none converted. This time I got progress and moved forward to the next step. It is buggy and they do a very poor job letting you know when you fail or what the clear objectives are, but it is doable and will progress forward. Good luck!

Technically, if you already have had it drop before, you can just pull it from Collections, like all other non-random gear.