That sounds very frustrating! However, this isn’t something we’ve seen before (otherwise we’d have squashed it already) - it sounds like it’s to do with your pattern of using Anvil. Can you give us any more information about what you’re doing when this occurs? Did it disappear mid-keystroke while you were editing, or when you next loaded the app? Obviously the ideal would be to describe a sequence of actions that always causes the problem, but any information you give will help us narrow this down.
PS: If you want to keep an explicit backup, there’s a much easier way to do this than cloning your app! Just hit the “Save Version” button on the bottom left of the editor, enter a label, and you can save a snapshot of your app with a specific name! That backup is preserved and immutable, and you can restore it at any time by clicking “View history”