WvW reward track bugs
If there’s a bug, it’s not with the reward track. You earned the armor box, you chose a skin — everything worked as it’s supposed to.
First, is there any chance you chose a similarly-named, but different skin? Assuming ‘no’, could you show a screenshot of your wardrobe, typing “mantle of the lich” in the filter? Be sure to start from the bank or a crafting station instead from the [h]ero panel.
Alternatively, provide the same details to ANet customer service — if there’s a bug, it seemingly is affecting only you (or at least, too few people to have seen it widely reported). Accordingly, you will need to work with them to resolve it.
John Smith: “you should kill monsters, because killing monsters is awesome.”