The "Search for Item" selection and the "/itemsearch" text command are the same function, just two ways of getting to it. I really like the suggestions for expanding where all it checks. Adding a graphical UI for it is less important, but would still be a nice-to-have.

The retainers' sell slots are the part that throws me off the most often. I've several times bought stuff I needed, only afterwards realizing I already had it but the search hadn't found it because I had it up for sale. But yes, it would be nice if, in addition to the inventory, armoury, and retainer's inventory that it already checks, it also checked retainers' MB sell slots, their equipped gear, the Armoire, your house or room, and the The Calamity Salvager's item reclaim. I also think that if you have withdrawal privileges from your FC's chest, that it should be included as well.

I'm less certain of whether the Calamity Salvager shops count. You don't exactly have those items, since it's just the right to purchase them there that has been unlocked. If they'd expand the search abilities to show both where you have items and where you can get them, the Calamity Salvager might be a better fit there.


Which brings me to a somewhat off-topic topic:
I'd like to see a general "where can I get this" feature added to the game, to show which items are purchasable, which are craftable, which come from gathering nodes, which are loot drops, which are quest rewards, etc. There are several out-of-game sources for that sort of information (lodestone, xivdb, libra eorzea, etc.), but not only is it more awkward to have that information be from an outside source, but those sources can't take your character's access into account. The Calamity Salvager shops only sell you stuff you've earned before. The beast tribe vendors will only sell you stuff if you have the right reputation with them. If something can be a quest reward, is that quest currently available to you? ...and so on. If something like the Lodestone or Libra Eorzea item database were incorporated into the game itself, it could have access to checking all those things.