Disappearing note content in Notes app

I was in the middle of adding to a note in the Notes app on my MacBook Pro when all but the most recent paragraph flashed as if selected and disappeared. My notes are synced across all of my devices, and now all of them have the same (now very short) content. This was the accumuiation of a year of almost daily journal updates, and I hate to lose that record of important events. Is there a way to access an iCloud backup from before this happened? I thought I was safely protected with iCloud, but I don´t see a way to restore the missing content.

A related but separate question- is there a maximum size for a note file, and a way to determine how big a file is? Perhaps this is a misuse of the Notes app, but I used it because it was quick and easy to access. Now I question the wisdom of that decision…