"On My iPhone" Notes Disappeared—How Can I Recover Them?

What are the steps to recover the "On My iPhone" folder in the Notes app on my iPhone 12 Pro Max running iOS 14.6?

It's not just the notes themselves that have disappeared it's the entire folder. And if you're planning to insinuate that it's my fault because it's impossible for this to happen, let me state for the record that nothing you can write will be one tenth as vicious as what my wife says to me on a daily, sometimes hourly basis.

With that out of the way, a solution would be most welcome.