Hi there. Shaders have to have been in your inventory or vault at the time Collections was implemented in order for them to be tracked and added. Being applied to an item doesn't count — just like how you must first dismantle a new item to get its shader before it gets added. Unfortunately year one shaders don't drop when you dismantle the item, so if you can't reacquire this shader, you'll need to get it to drop from Bright Engrams or buy it from the Eververse Store if Tess sells it.