Those are all things I've experienced before with some regularity (though not, fortunately, any significant frequency). I seem to experience it most strongly when overtired, though it will still sometimes happen when I'm perfectly awake and well-rested.

But it's strange, all the same.

Though, mm, part of me wonders if it's somehow related to the way the brain processes information. You know, when you're wearing socks, you're not consciously aware of the feel of the socks all the time (well, most people aren't, anyway--let's assume for example's sake). You'd go mad if you were fully aware of every little sensation all the time, so the brain blocks out anything unnecessary. I wonder if sometimes, when I'm not using parts as much, my brain decides it doesn't need to acknowledge the pieces not in use, thus resulting in experiences like the ones you mention.

Curiouser and curiouser.