Summary:
You cannot configure a report to show the list of users who have not entered/saved any time for a given timesheet period. This cannot be achieved with a report as there are no parameters that can be set for the data to be processed.

Work Around:
Use historical timesheets and filter the data for un-submitted timesheets and sort by the save date. The timesheets that do not have a save date (blank field) would be the ones wherein the users have not entered time. This can be also be printed using the browser printing option.