STV (or STC, etc) are delisted on Mondays following the "drop" in US stores, or premiere on TV. They will be on the calendar.
3 Years on the Shelf....these are Wrapped projects that are not getting released. Ususally on a Friday with no notice. Most are indie projects that did not get a distributor, or have a distributor who is just not going to release it.
What was originally asked about are the abandoned projects. They are always in concept stage. The delists occur from time to time, on a Friday, with no notice. Occaseionally, a well known project that has the plug pulled by the studio might get a quick delisting. Disney's NEWT comes to mind as an example. On the other hand, during the fight between New Line and MGM over , HOBIT was a concept, so you never know.