If you have a backup of those notes, then you shouldn't have a problem. So I'll ask the obvious dumb question:- Do you have backup of those notes?
I had my notes backed up to my email account, but not hers. I mistakenly thought I was going to join our notes together like I usually do with other items and then back them all up. There was no warning beforehand that it would overwrite everything. When I airdrop groups of photos to my iPad or groups of notes to the apple note taker, I've never had it overwrite anything. It's a shame that I was able to wipe out over two years of notes in half a second with no warning.