Yes, as a kid, people would wave their hands between my face and the book I was reading, and I wouldn't notice. We also had a rule in the house, that if I did not respond to something one of my parents said, it meant I hadn't heard it, and for them not to get mad at me when I didn't do whatever it was they asked me to do. They had to keep calling my name until they dragged me back to the real world, and then ask. The one problem with deep focus, which I have recently discovered, is that, because the brain starts switching off input receptors to free up processing for the focus, you can injure yourself and not be aware of it.