Notes on my iPhone are gone!

I was able to make the folder visible again; but all the notes are gone. I have no "Recently Deleted" folder either. How could this happen and can I recover them?

For further info, I usually use "Notes on my iPhone" because you can lock them. Overnight, that notes section got toggled to off somehow in settings. When it toggled it back on, all the notes that were in it are GONE.