I have playlists that exist in ~/.kde/share/apps/amarok/playlists, but do not show up in the playlists pane of Amarok.  If I reload the files in the playlist and attempt to save a new version of the list, Amarok asks me to confirm an overwrite of the existing playlist.

If Amarok can see these playlists, why don't they show up in the playlist manager?

have you tried using the playlist menu to import those playlists? It sounds like you've trashed your collection at some stage but kept the rest of the ~/.kde/share/apps/amarok/ directory.

What sort of behaviour does "trashed" describe?

The playlists that exist and and are not being seen were created over multiple Amarok sessions -- so if trashed means some kind of system crash, that has not happened on a regular basis.

I have not noticed any strange behaviour with Amarok (have been using it for 2 weeks now).  Is it possible to unknowingly trash it?