It is important to note that student assignments will disappear from Moodle 16 days after the enrolment end date.You should ensure you have downloaded and saved all marked assignments before that deadline.
If you should need to retrieve a student's data, you can manually re-enrol the student into the Moodle course and download their assignment(s). Please remember to un-enrol this student when you have downloaded what you need. If you need assignments from a whole class, you will need to manually re-enrol every student in the cohort.
Reference:
Retention of Assessment Materials
Download/Backing up Quiz and gradeshttps://moodle.unitec.ac.nz/mod/glossary/showentry.php?eid=635
Download/Backing up Turnitin Assignment and gradeshttps://moodle.unitec.ac.nz/mod/glossary/showentry.php?eid=603
Download/Backing up Moodle Assignment https://moodle.unitec.ac.nz/mod/glossary/showentry.php?eid=636
Download/Backing up Moodle Gradebook https://moodle.unitec.ac.nz/mod/glossary/showentry.php?eid=637
» Guide to Moodle