Yes, I am very subject to that. It can be while I'm on the computer, or reading, or in my daydream universes, watching TV, or while doing anything else that I get engrossed in. When I was still able to work, it also happened on the job, as I would sometimes get very focused on the work, and everything else would be in null space--or maybe I was. 
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If a man does not keep pace with his companions, perhaps it is because he hears a different drummer.
Let him step to the music which he hears, however measured, or far away.--Henry David Thoreau