I think there was a bug I saw go by related to this. IIRC there is a combo of being non-semantically tagged and the Item having metadata that makes it not show up in the Item picker. If this is the case I think the only way to work around it is one of the following:
upgrade to the latest 4.2 snapshot or at least the latest 4.2 milestone release
add a semantic tag to the Item, at least long enough for it to show up in the picker
open the code tab and manually edit the Item name from there
But don’t forget to make a copy of your rule as a backup.
And: To filter items you have to first select “show non semantic” and then enter your filter. The other way around doesn’t work.
I have no idea if it’s fixed in 4.2 but the Item picker is the generic one used everywhere in MainUI, right? There was an Issue and PR that changed something like the problem reported here. So it’s probably fixed in 4.2 but I’m not running 4.2 and even if I were I don’t have any items that are not showing up so probably couldn’t great it anyway.