Ok...so I have been having an issue where every time I beamed down to....well anything, my basic attack for whatever weapon I had equipped would be missing from my hotbar. I'd drag and drop it back on but the next mission...gone again. Finally the last straw was when both primary/Secondary attacks kept disappearing.
Finally fixed it by unequipping both weapons, beaming up, beaming back down, placing the basic left and right strikes onto the bar, beaming up, and beaming back down. Then I could re-equip my weapons and the primary/secondary attacks would finally stay on my hotbar.
So hope this helps anyone else this happened to, and Devs please make note of this for a fix.