If your current course seems to disappear, it has most likely changed status from "In-progress" to "past." You will be able to find all of your courses by going to your avatar in the upper-right and using the drop-down to get to your profile. Another way is to use the filter on the Dashboard to view your past, in-progress, or future courses. If you still cannot find your course, it could be that it has been hidden by your instructor. They will need to unhide it in order for you to access it.