If you are not a Communist Youth League member, but you used to be a Communist Youth League member, the information of the Communist Youth League member remains. Some organizations can help people who are not members to inquire about their members' information. For example, if you go to the original school to check, if you are a member of the Communist Youth League in junior high school, it will be recorded in your personal file when you enter high school. Of course, neither junior high school nor senior high school has joined the League. Only when the university becomes a League member will it be recorded in the personal file. As long as there are documents, you can find them.
If you need specific help, I suggest you consult the local Communist Youth League organizations or related organizations for more detailed information.