Can I get a page, file, event, etc. back once it has been deleted?

Unfortunately once an item has been deleted it cannot be retrieved.

It is very important to backup the content and files you have on your site.

You can use the Archive Record icon  in the top right corner of the screen to email a copy of the contents of the page you are working on. The email is sent to the email address listed for whomever is currently logged in. You can be sure the email address is correct on the Admin Profile tab of the Account manager (if you don't have People manager) or in the appropriate profile within the People manager.