IF you had named the document and saved it immediately on opening it, macOS would, assuming you have Time Machine running, have immediately begun saving an updated version of that growing document at intervals wll under half a minute apart.
Without that initial save (or any save since opening the document), macOS has no instructions regarding what to call it or where to save it, so the repeated saves never get started.
When you closed the document, you closed the only copy, leaving nothing to be 'recovered.'
Suggestion for future:
- Open a new document.
- Immediately give it a name, tell Numbers where to save the document, and do a Save.
THEN start writing.
Regards,
Barry