A few years ago now, I was in Apple Notes looking at a few dozen discrete notes that I’d created while attending a conference. Suddenly, I became aware that, one by one, the notes were disappearing. They were quite literally being deleted, one note at a time, until finally every last note – many with dozens of lines of text and many with dozens of photos – was gone. I knew enough to search for them in the Finder in whatever twiddle Library folder they were stored in at the time, but they were no longer there. And they were no longer on my iPhone or my iPad, either. And they weren’t in my Time Machine backups from the relevant time period.
I have used neither Notes nor Time Machine since.