All my notes disappeared after the new update download

I hadn't realized this happened until my boss came to me with the problem. He's technologically challenged so I created a couple notes for him a few years ago with hints to passwords, etc. He uses these often and came to me last week to ask where they disappeared. I looked and, sure enough, no notes on his Notes app. So I checked mine because I had several notes referencing wines, books or authors, etc. and they are all gone. No notes. Elsewhere, I found someone referenced checking Settings>Mail, Calendar and turn notes off in your email (a spontaneous and unwanted change Apple made through an update!) and they would reappear. They did not. There are no notes folders in any of my email accounts either. As well, under Settings>Notes, "on my iPhone" account shows as "on", I assume, since it's green, but it is a faded green and can't be moved to an off position or on position. These notes go back to my first iPhone and have successfully updated to each phone since only to be lost now!

Check this and see if it helps:

Upgrade your notes with iOS 9 and OS X El Capitan - Apple Support