In phabricator.wikimedia.org I search for: KB
The search finds the task T125316.
"No results found for this query."
It would be nice to fix that bug.
This happens because we cutoff words shorter than 3 characters (or 4? I can't remember offhand. It's 3 or 4. Anyway...). Ideally, Phab could let you know that you've searched something we couldn't even index to begin with, and provide a more informative error message.