On Outlook there is a box on the left of the screen that lists Folders, Inbox, Junk, Drafts, Sent, Deleted and New folder. If your is the same just click on deleted and send it back to your inbox.
On my home and my work emails, when you delete something it goes to another folder - deleted items. At home it stays there forever unless you go in and delete what is in your delete folder. At work it stays in the delete folder for a day or two and then automatically really deletes. I have never had emails that the first delete really means they are gone.