A lot of songs in a playlist are gone

[radiotsar]

I have a playlist "Starred" that I had saved 3000+ songs to, everything from bands with names that start with numbers through ZZTop.  I just found today that everything prior to Randy Newman (alphabetically) was missing.  I have started transferring some of the songs that I had in other playlists, but it does not contain all the missing songs.  Any idea what happened and how I can fix it?  I doubt that more than half my playlist would suddenly become unavailable.