Objects created by users are stored into .Shared files in the same folder where the QVW is stored. First make sure those .Shared files are not deleted.
But this also means that depending on several factors, among them, server license, security, authorization and document availability, the user might be able to create them but not to save them. Make sure that everything is set all right in the QlikView Management Console and that filesystem permissions are granted accordingly.
If you have a backup, you will need to stop QlikView services, then restore the .Shared files, then restart services again.