This is something that's annoyed me slightly, too. I wish the player worked more like a Unix filesystem where it would delete the data if it wasn't referenced anywhere instead of this all-or-nothing deleting.

Anyway, the tracks are still there, not referenced in any playlist.

Go to the advanced search and type in ``refs=0''. This will return all the tracks on the player that are not referenced anywhere. You can then delete them from that screen.