If you start creating a deck, or if you are editing an existing deck, and you leave before publishing it, your deck might not show any more on the site. This is because it is in edition mode and is not considered to be ready for public viewing. But you don't need to worry. You only need to try to create a new deck, and you will be presented with the latest one you were editing so that you can finish it. Then you can publish it so that it goes online.