I sifted through the names of all the files in the texture.kfs file and looked at the files that popped out at me -- stuff with "ui" in the name and other things that weren't immediately clear. It turns out, the icons aren't in there at all! The UI textures are actually in data.kfs instead, with the filenames tex1.dds through tex11.dds (the item icons are in 8 and 9 specifically).
The right car, on the right street... in the wrong town.
(EDIT: You'd think proofreading a paragraph wouldn't take a half hour, but sometimes, it just does.)