How to un-delete a collection
Deleted collections are soft-deleted for 28 days. You can undelete while a collection is soft-deleted:
Log in and go to Control Panel > My Images > Bulk Delete Collections.
At the top of the page, click the link "soft-deleted collections"
All soft deleted collections are highlighted. Click the checkbox to the right.
Scroll to the bottom of that page and click "Recover Collections".