Noticed this while visiting Banshee - Austringer cannot be given a Deepsight Harmonizer, when other weapons from the same season can (note the Tears of Contrition Banshee is also selling). EDIT: At no point did it cross my mind that the reason it's not showing up on the weapon is because I already have it crafted - which I do. My apologies.
You have the pattern already completed so the slot wont show for you. You haven't finished the tears of contrition pattern so thats why that slot is showing.