It's pretty common to run across old braided jacket NM cable without a ground. It's very rare, in my experience, to run across NM cable with a thermoplastic jacket that doesn't have a ground wire of any sort. Often, you'll find the plastic jacketed NM cable with a reduced size ground. Very seldom do you run across plastic jacketed Romex without a ground, but I did today. Just a piece of paper interleaving, tightly wound, where the ground would normally be. No ground inside that brown paper at all... just a twisted rope of paper. I saved a big piece, and took some pictures and scanned in the jacket labeling. I wonder what years this stuff was used? I would have to think that it was just a very few years.