Actually, it shouldn't be that hard at all. There has to be a DB somewhere of "all the places that reference this song" (a lack of any, and an existing file, gets you into the "Unattached Items" folder). Basically all the feature request is is "what are all the playlists which reference this FID", but done recursively (to also say, "OK, that playlist.. what are all the playlists which reference THAT?" until you get to the root playlist)

D