Hi there. In order for a year 1 shader to be unlocked in Collections, you had to have at least one copy of the shader consumable in your Inventory or Vault after Collections was introduced with the launch of the Warmind DLC. Items with a shader already equipped do not unlock the shader from Collections. You would have to reacquire the shader by itself from the Leviathan raid chests or from dismantling an item with the shader applied while the Leviathan raid was still available. Year 1 shaders can no longer drop from dismantling items they're applied to, so unfortunately there is no way for you to reacquire Calus's Selected. You will have to wait to see if it's brought back in some other way.