Even with the "Also search sub-categories" checkbox checked, searching does not find images in sub-categories.
Example: Search
my gallery - category = "modern Japanese culture" (near top) for "kimono" and you will find several photos. Now do same search on parent category = "Modern Japan" and it finds zero photos. This is typical of all categories except "search all categories" which does find all.
Also, on the search subject, keyword links are not working (does not find same keywords) as indicated in a previous thread.