If you've accidentally deleted a folder, page, or file and you'd like to get it back you're in luck! The CMS includes a recycle bin, which stores deleted items for 30 days before they're permanently deleted.
The first thing to do is navigate to your desired site, directly under the title "Site Content" you will see a link to trash:
Within the trash you will see any assets that can be restored. Select the checkbox for the asset and then hit the restore button.
You're asset will be restored. Be sure to re-publish the asset and areas of your site affected by the restoration.