Most recent numbers file version overwritten by older version

Hello,

I was working with a numbers file since couple of months. Suddenly, beginning of October my file stopped being synchronised with icloud, nevertheless I could still work with it on my MacBook. In between I was closing the Numbers application but was always able to work with the latest version of the file. Today however, after I have opened the file, it shows the version from the beginning of October. All changes done in the past month are gone! I cannot even select any previous version other than the one from beginning of October and earlier. How can I retrieve my changes back???