Hi there! Are you maybe referring to a campaign that you accidentally deleted? You can definitely restore this by clicking on account up in the upper right corner and then selecting deleted items from the drop down menu. Once the next page loads, you'll notice a tab titled campaigns. Click on this and you'll be presented with a list of all your deleted campaigns. Here you're able to sort those campaigns by deletion date and I see one untitled mailing which was deleted this morning. Click on the down arrow to the far right and then click on undelete this item. Now once you head over to your campaign page you'll see that campaign is back!
Hopefully this is what you're looking for, but please let me know if I can assist further.