Opening ~/Library/Mobile Documents/ will cause a window to open with title "iCloud Drive".
To attempt to retrieve an earlier version from Time Machine, don't open it. Instead, navigate to ~/Library using the same technique, then "Enter Time Machine". Then, open Mobile Documents. Its contents will have unexpected names. In the case of Numbers look for a folder named com~apple~Numbers.
Open that folder from within Time Machine, then open the Documents folder within it. Determine if you can find a copy of your document. If you can, do not click Restore. Instead, control-click (or two-finger tap) the document. In the contextual menu that appears, choose "Restore (document) to...". The Time Machine interface will close and you will returned to the Finder, which will ask you to designate a location. Choose one such as your Desktop.
The reason for doing that is I suspect restoring a document to that same folder may corrupt the iCloud storage database. That will probably repair itself but why ask for trouble.
I don't know if this will help. The best you can possibly hope for is to find an earlier, Time Machine version of your document that Numbers will open, or for your latest readable version to spontaneously reappear in iCloud, so if you do manage to retrieve a readable copy keep it separate from iCloud for now.