Hi Lesley,
you could use the Portfolio Analyser for this.
Create a report where all resources are on the row, on the header choose
your time dimension. (make sure that you set up the report so that you can
see all resources, also the once with a value of 0).
As a value you choose actual work. all resources with a value 0 for a chosen
time period are those that have not submitted time.
Hope this helps