1, ask the library staff for advice. You can go to the library to consult the staff, explain the situation of returning books, and ask them to help you check the borrowing records and returning books. If there is a problem with the system, it will help solve the problem.
2. Provide evidence to return the book. If you still have a library certificate or other evidence when you return the book, you can take these certificates to the library and ask the staff to help verify them.