If your Schoology course has gone missing it most likely was attached to an open grading period which was removed as part of an organizational wide cleanup of our Schoology course catalog. Below is a video showing how an archived course can be accessed again:
https://tcalearn.com/ViewArchivedCourses
If you believe your course was not archived but instead was deleted it can be accessed via the link below:
http://tcalearn.com/RestoreDeletedCourses
If you have further questions you can reach out to Kevin Pressley at kpressley@classicalacademy.com who can assist you. Thank you!