I added "refs" count in Emplode as a displayed field. So I can always tell if there is more than one reference of that song floating around. Sometimes it can take me a very long time to find that ofher reference though!

I think it was Peter that gave me a tip to help with this. If you delete that track with the box checked then do a search for "changed=" you will get a list of all playlists that were effected by you deleting that song (assuming that is the only thing you did during that sync).