i found this:

"When no courses are favorited, the courses list automatically displays up to 20 courses alphabetically in the drop-down menu. However, once you have selected at least one course as a favorite, only your favorite courses will appear in the Courses list."

and since none of my semester's active classes have been published yet (so i'm unable to star any), this may be why i'm still seeing old classes that i've "un-favorited."