While using NaturalHR the situation might arise where you may need to view an archived employee's self-cert/return to work forms. In order to do so you'll need to Restore the archived employee by navigating into People -> Employees:

If you're using Card view as your default employee view click Other Actions -> Table View.

Once in table view search for the employee's name and click Actions -> Restore. Once restored you can navigate to their employee profile -> Time and Attendance -> Time Off and locate the time off instance which the self-cert/RTW form is linked to and click Actions -> View Return To Work/Self-Certification.