Dear Basil Ben,
Thanks for visiting Microsoft Community.
I understand that you are having synchronization issues with your home account, OneNote, which is causing file loss.
Due to the limited information I have learned, I am unable to provide you with accurate advice and I need to confirm some information with you in order to better understand and resolve your issue:
Are you able to see the lost notes in the web version of OneNote? Can you see the OneNote notes on your mobile device?
Can you see your OneNote notes in OneDrive?
If you are only unable to see your notes in the OneNote desktop app then this is not your cause, there are many users in the community in many areas who have recently reported the same issue as you and a product manager on the OneNote team has indicated that this is a known issue, you can check his response from this thread.
OneNote sync failure error code:0xE00009C8 bb0ur - Microsoft Community

Best regards
Miyeon.S - MSFT |Microsoft Community Support Specialist