Continuing the discussion from Note disappeared:
I have just discovered that part of the problem of the ‘disappearing note’ was that I inadvertently pasted a page of text into the title of a note. As the first line of the pasted text matched an existing note title, I didn’t realise.
It would be helpful if attempting to paste text which includes returns or line breaks, was not permitted and triggered an alert.
(I only discovered this when looking at the project with all notes collapsed, and noticed the three dotes indicationg a collapsed note were on the far right of the title, not at the end of the text.)