Hello @TQ ...
It sounds like you might need to get your school's Canvas administrator or someone from your school's Online Learning / eLearning / Distance Learning department involved with this request. There might be a way for your Canvas administrator to retrieve the course using the information in this Guide:
How do I restore a deleted course in an account? - Instructure Community (canvaslms.com)
If you do not know the Course ID number, you should be able to log into your school's "test" or "beta" environment where you might still be able to see the course in an undeleted state. Then, you could look at the course URL to determine what that Course ID number is (the number following /courses). Here is some information on these two environments:
Just be sure to log out of these environments when you are done...as these are not the regular environments that you normally log into on a daily basis. (That environment is typically called your "production" environment.)
I hope this will be of some help to you. Let Community members know if you have any questions about this...thanks!
