If you deleted one of items accidentally or simply changed you mind, you can use Deleted items option to correct that mistake and undelete it.

When you delete an item, it's not actually deleted; it's rather marked as deleted so it doesn't show up in standard user interface. If you choose to revert item back it will contain exactly same data as before deletion.

 

Use Undelete option to restore item, Delete permanently to remove selected item physically and Empty deleted to remove all items physically.