I acquired the Forerunner sidearm and completed the quest, but when I went to claim the 30th Anniversary Triumph for the seal, it said I hadn't done it yet.
When I went to the quest archive kiosk in the tower, I could pick up the quest, which said I was only at step 3/6. However, that step requires me to get the key from Xur, but I can't acquire it for a second time.
So, here I am, literally holding Forerunner while the game tells me I don't have it yet.
Can someone please help? It's clearly bugged.
This is a known issue Bungie is investigating.
https://www.bungie.net/en/Forums/Post/260156995?sort=0&page=0
[quote]The Paraversal Prize triumph does not unlock after acquiring the Forerunner Exotic for some players[/quote]