Since you didn't tell what app you used to make that notes, it's impossible to tell. Next stop: the customer service of the maker of the app.
And a suggestion for the future: do a regular backup of what you don't want to lose. And then use a backup program, not a program that only synchronises a deletion to the cloud, or whatever the data is backed up to.
For backup, nothing really changed since we made a copy of the diskette our data was stored on to another diskette, back in the 19-eighties. Just to protect ourselves against accidental deletions, diskettes turning bad or lost, or viruses deleting them. After 40 years, people should have learned keeping their data safe.