Restoring a campaign?

Hello Jikard, After a browser refresh, you should find that campaign back and available on your account. To answer your other question, there is no way to transfer ownership of a campaign to another user (This is a copyright prevention measure). The only thing you can do is promote one of your players as a GM to take it over, but the campaign will still be under your direct control and you'll need to keep it and whatever custom content you uploaded to it available for their group's continued use.