Lich didn't drop the weapon

[(PSN)Eyes_Of_Tiamat]

Got a lich with Ayanga from a friend, vanquished it and did not get the BP. Anyone had that happen? 

[(XBOX)R3d P01nt]

Are you certain you selected Vanquish and not Convert (or whatever the other option is)?

I would check your foundry and ensure it's not there (take a screenshot).  Check your arsenal to show it's not there (screenshot).  Check your inventory to show it's not there (screenshot).  Check your codex to show that you did defeat the lich and you did vanquish it (screenshot).  Send all of these to support and see if they can add the weapon to your inventory.