Geez, that is exactly what happened.
When I started up Evernote, it unexpectedly asked me to sign in. To sign in, it asks for an email address. But, I had a user name, not email address (I signed up in 2013, I guess that's how they used to do it...) . So instead of just putting in my user name, I figured I needed to enter my email address--- which no doubt created a new account for me with -0- notes.
I just tried signing in by putting my user name in the email field--- along with the password-- and violà! all my note/books are there.
It would have been helpful if the Evernote sign-in field said "Email or User Name", for us old-timers that signed up with a user name.
Thanks to all!