OK I got it now, and I'll tell the secret in case anyone else gets stuck like I did. If you press the home button a little too long it will lock the function, but if you just hit it briefly it will go to menu. I've intuited how to do both functions before without realizing exactly what I was doing but not today.
I didn't see where this slight difference in function for this button is explained anywhere, it's a wonder I ever figured it out the first time. Today it took hours before I happened to hit it just the right way.
Big laugh on me.