Often times there are instances where an email item is inadvertantly deleted, the trash is emptied and the item is lost forever... or so one thinks. In truth there is a period of time, presently about two days, where items are retained in the mailbox but not exposed to the owner of the mailbox. This setting enables the recovery of cases just like this by the end user without IT interaction. Here are the steps to recover an item you inadvertantly deleted.
Open Outlook and select Tools -> "Recover Deleted Items"
In the window that opens locate (select) the message you wish to restore and click the "Recover Selected Items" button in the upper left corner of the screen. If there are multiple items you wish to recover you can hold the control button while clicking to select multiples.
After a few seconds the items will be recovered to your inbox.