I experienced this for the first time a few days ago: Wanted to edit a food which was missing sodium facts. When I edited it and confirmed I could not find the food anymore in the database. Also created the food then to be able to add it to my diary but after creating it it did not show up either or it said that the food already existed (can't remember anymore).
Nevertheless, just wanted to edit and add saturated fat facts to an item and now it's gone again. Can't find it anymore in the database.
Has anyone experienced the same? Would be great if MFP can fix that.