Welcome to the forum, Ché. Your project is not really lost, but it is ending up in a folder inside your iCloud Drive that is unhelpfully hidden (for reasons that are not really clear to us at this stage, and Apple’s developer documentation is frustratingly vague on this point).
If you have a Mac, you should find that the project is synced to the iCloud Drive folder on your Mac, and if you’re really lucky, you may find that there’s already a Dorico folder in there visible in the Finder, in which case your project will be in there.
If you don’t see the folder in the Finder, you can nevertheless find it using the Terminal. I describe the method in this post:
We are indeed working on these issues at the moment, and we will announce news of updates here on the forum and on the Dorico blog.