To access content that has been deleted, you will need to do so through a hidden page called Undelete.

You can get to the undelete page by deleting everything after your course number (every course has a unique number) and by adding /undelete to the end of the URL. Then click enter.

For example:

^{On the modules page, delete /modules.}

Replace it with /undelete.

List of Deleted Content

On the undelete page you will find a list of deleted content. Click the restore button if you wish to recover that item.
Now, if you return to the course, it should be restored.

Worth noting, that a restored item may not automatically function properly. Connections, such as links, may be broken between it and the rest of the course. Make sure to double check all links and check that settings are still correct.