Lost Weapons After Patching/ Phantom Liberty

[Your Mom's Favorite]

As the title states, I've lost Weapons to include Legendaries after the update. I haven't played in a while and it seems my items are missing.

[Mei]

It is heavily recommended to not use an old pre 2.0 save on 2.0. Losing some weapons is the least of the problems you could encounter.

[Your Mom's Favorite]

Sure, doesn't exactly change the scenario though.

[Maviba]

That's normal and was announced to be supposed to happen.

V 2.0 overhauled the entire perk and crafting system, so some old (weapon- / armour) mods simply don't exist anymore and therefore don't work on old saves as well.

It's not like the weapons got just removed from your inventory. But also the story progress affiliated with those weapons got reseted.
So all you need to do is restarting those missions and you may earn them back.

Good thing is: most legendary weapons are still in the game.
But you need to redo the corresponding quests in order to obtain them.