You said the filter would find something if I had it. I gave you an example of how it wouldn’t find something I had. Heck, if you want another example of it being unable to find something you have, if you have a non-English client, and you search for the exact name of something you know you have, it’s case-sensitive as to whether it finds the item or not, unlike the English client which is case-insensitive.
Not only is the filter / search badly implemented, it also starts with focus when the inventory opens. The default key for closing all active windows is SPACE. This works for all other windows / dialogs other than the Stash, which now puts the spaces into the filter textbox instead.
On the PTR which first introduced the filter, the issues of taking focus, case sensitivity, not finding gems that were socketed, and the inability to search by class of item (e.g. “dagger” would find all daggers) or rarity of item (e.g. “primal” would find all primal ancient legendaries) were all given to the devs. All the feedback was ignored, and we got the focus-stealing filter we have now that’s incapable of finding items you actually have, even if you type in the exact name of the item you have.
Short version: good idea, badly implemented.