Hello @mark_korell ...
For the course in question that your colleague seems to be missing, is she enrolled as a "Teacher" in that course? Also, is there a text box next to the drop-down list where you normally select a course? If that text box is there, has your colleague tried to type in the name of the course or the course number into that box to see if any search results come up?
Looking forward to hearing back from you soon...take care, stay safe, and be well.
Thank you for the reply. We found out that her date for the course had been changed and it ended. Her course was located in the "Past Enrollment" section.