I open the Sound preference pane multiple times a day, and for the past week or so, it will randomly stop showing up in Alfred until I rebuild OS X metadata. 'Sound' shows up consistently in Spotlight.
So far, this has happened 3 times, and Sound is the only thing I've noticed disappear from Alfred. Other preference panes are there.
I'm on Alfred v2.1.1 (227), OS X 10.9.
Thanks