To update the pages to re-appear on their specified department pages, you can use the Purge Date Updater function within the Control Panel to update the purge date for all of the pages at once, instead of one at a time.
Within the Purge Date Updater,
- Select/highlight the pages you wish to update
- Enter in the new purge date (far in the future)
- Click "Change Purge Date on the Selected Pages"
You may need to refresh your pages to show the updates pages or run a Site Rebuild to push your newly changed pages dates through.