Hi FS,
Welcome to our forum!
Here are some steps you may take:
- Switch to the old version of Outlook from the Help menu or toggle New Outlook from the top right if available.
- At same time, to confirm that the notes still exist, please go to Outlook on the web>Notes to check if they exist on OWA.
- Use Outlook's search box to retrieve notes by typing the words included in the disappearing notes.
- Check the deleted folder for missing notes and select all items you can to restore.
Hope it helps.
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