It appears in course list, and I did not hide it on purpose
It's likely that the term is over for that course based on the dates set by your local Canvas administrator. This course has become concluded for you and so Canvas has removed it from your automatically-displayed list of courses.
If you had marked the course as a favorite before it had disappeared, then it would not have been removed when it expired (according to the documentation). You can unfavorite a concluded courses, but there is no way to favorite a course that has concluded for you.
To get the course favorited at this point, you may need someone (your Canvas Admin) to help. The process involves unconcluding the course, marking it as a favorite, and then re-concluding the course.
If you can go to Course > Settings and change the end date, you can do the process yourself. Set the date to the future and save the settings, then go to Courses > All Courses and favorite it, then go back the Course > Settings and set the date back to what it used to be. If the instructor cannot override the date, then the Canvas admin would have to help out.
If you are unable to change the date in Canvas, you can still get to your course by going to the Courses > All Courses menu. You can then add a bookmark in your browser to go directly to the course. It's not the same as being favorited in Canvas, but it is something that you can do without help.
Canvas has a lesson in the Canvas Instructor Guide on how to favorite a course. The information at the bottom of the page talks about what happens when a course is concluded: How do I view my favorite courses in the Card View Dashboard as an instructor?
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