This is a post by Beth stackpole on PTC site.
Sometimes a drawing in PTC Windchill will reference a part that doesn’t exist. These “ghost objects” are relics from the original CAD file—typically a dummy that’s no longer relevant. But while PTC Creo doesn’t seem to reference the old model anymore, PTC Windchill just won’t forget about it.
This year at PTC Live Global in Nashville, Tennessee, veteran presenter Justin Roegner will address how to rid your system of these artifacts as part of his talk, “Little Known Tricks for PTC Creo Parametric.”