Ya, I think that's what I fear as well. I get into a sort of tunnel vision when I'm focused. Some of my colleagues have mentioned that they have stood at my side for a minute or so(I have a slight reputation ;) ) and I don't feel that there is anybody there. When they finally do tap, it's all the more jarring.
I'm well known for jumping about a foot in the air when tapped on the shoulder. I despise workspaces where people can walk in behind me. (Hello cubicle!) When I'm in the flow though...
Aggh, I'm getting paranoid just thinking about someone walking in behind me now. Working when nobody else is around and no phones can ring is the best kind of work.
