When a resource leaves your company, you should always make sure that all timesheets for the resource are processed before making the resource inactive and removing their credentials from the system. If you find yourself in a position where you have already set the resource to inactive, and you later discover that the resource has unprocessed timesheets, you can resolve this situation by executing the following steps:
1. Edit the User and set the account status to Active
2. Set the User logon account to an active AD account
3. Select the Prevent AD sync option for the user
4. If necessary, add user to PWA Team Members group
5. Add the user to the SharePoint Team Members group
6. You can now either logon as the resource or its delegate to remove the unprocessed timesheets.
7. When you are done, edit the user account, remove the AD credentials and set the account status to inactive