If you feel as though you’ve “lost” a course on your My Progress page (usually history or literature), make sure you click “Show Details” next to the history or literature requirement. Student Planning hides these details once you have finished the particular section. It’s most likely just been “hidden” and you need to click show details.
However, please remember that classes can’t be used in more than one area, so if a class isn’t showing up in one area, it’s most likely being used in another area.