Hey there, Collections tracking went live in Season 3, and fully implemented when Forsaken launched. For an item to be added to Collections it had to be in your inventory during Season 3 at the earliest. Any item earned in Seasons 1 or 2 that was deleted during that time, would not count and had to be re-earned. You never played during or after Season 3 until recently, so that sounds like what happened to the boots - earned, deleted before collections tracking went live, and never re-earned at a time when they could be before the raid's removal. If you didn't delete them during S1 or S2, you'd still have them on your character when you got back into the game recently. For shaders, they had to be an unattached copy in your inventory - it is not enough to have an item with them applied. So if you earned the shaders and used them, that would be why they never got added to collections.