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).

That's the other way round from the database in the car player, though. Emplode has to build that inverse database from the car player's one; that's why only emplode, not the player, puts things in Unattached Items. (It'd be a waste of precious memory to have the database in the player both ways round.)

The player only knows the children of each (playlist) FID, not the parents of each FID.

Peter