Not to be confused with the following question, which deals with the obligation to follow laws that are mentioned in the Talmud but are not mentioned in the [Rambam and] Shulchan Aruch.
If a law is in the talmud, and not in the shulchan aruch, then is it followed, or not followed?
I seem to remember that there is a sefer that goes through Shas, and notes all the laws that were omitted by the Rambam and/or the Shulchan Aruch, and discusses why the codifiers didn't mention these laws.
Does anyone know the name of such a sefer?