It looks like we don’t have an item source for that item, which is why it doesn’t show up in the list for “Add to my bag”. We’ll add a source, seems like it is a delve item.
As for why it’s not showing in your great vault ranking… the issue is that you do not have an off-hand that could be paired with it in your inventory, so it doesn’t have a good way to rank it…
The Great Vault, Catalyst, Valorstones/Crests, and Add to my bag searches can only rank an item if a valid gear combinations using your current inventory could be created. We do not currently allow a gear combination with just a one-handed weapon and no off-hand. Even if we did rank it with a blank slot… the score would be pretty bad and not representative.
Thanks for updating. And yes, it’s understandable you hesitate to rank an empty slot. I guess my task would then be to add an potential offhand-item and see how the main hand would fair then…