You should always receive an e-mail receipt when submitting your assignment in Moodle or Turnitin.  If you have not received one check that you have submitted your work properly.  Submitted work will have a status of "submitted for grading", whereas work that hasn't been properly submitted will still be showing as "draft".  If it is still showing as "draft" did you tick the box to confirm the work is all your own and then confirm submission?  Missing either of these steps will mean your work is not submitted.

If you have completed all the step and your work is showing as "submitted for grading" check that your e-mail receipt has not gone into your junk folder.

It is recommended to submit in good time to allow for unforeseen circumstances e.g. Wi-Fi/internet issues.  Failure to follow these instructions may result in your work being returned to you, or cause a delay in your submission which would be regarded as late and subject to penalties.