Once the item cfg is gone then your cant get it back unless you re-download again and it gives it back to you. Did you completely delete it from your Trash bin as well? If not then get it back. All you really need to do is get ride of everything except for "Christmas hat" which is already preloaded on the game when you first download it.
You may edit your item cfg by opening it up in notepad and delete not everything in there.