Your inventory was most likely full when you turned in the quest. Exoctic Cyphers only go to the player's inventory, so if it's full the Cypher will be lost. Lose items cannot be recovered, you will need to get another one next week or from the Season Pass rank 55. [quote]Deleted Item and Character Policy Whether due to accidental deletion or unauthorized account access, Bungie does not recover manually deleted characters or items, and does not replace in-game items that are lost or dismantled. Bungie does not provide the following services: [..] Recovery of items lost due to Player Inventories being full https://help.bungie.net/hc/en-us/articles/360048717732-Deleted-Item-and-Character-Policy [/quote]