My intention was not to bash you only to point out the procedural error.
No worries, no offense taken.
I would like to explain my actions a little bit though, not to justify them, just so you know how I managed to make such a 'simple' error.
My speed control knob needs to be turned a reasonable distance before the motor starts to 'hum' then turn, so I assumed it was cutting the power when fully turned off. I assumed it worked somewhat like my variable speed hand drills - they have a switch for forward/reverse but not 'off'. I think nothing about grasping the chuck on one of them, as long as the speed control is at zero. (Now that I type it, I wonder if I'm wrong in that as well...)
Anyhow, that's how I arrived at my incorrect conclusion. With zero training, it was actually an easy assumption to arrive at. I'm going to really take a careful note of all the actions I do in my shed, just to make sure there's no other potential hazards that I'm exposing myself to without thinking about it.
One last item of interest - when it happened, it was far from the first time I've moved the chuck in exactly the same manner, it's just the first time I had an issue doing so. What this tells me is that just because you've gotten away with a hazardous operation in the past, doesn't mean you will always get away with it.
Stay safe everyone!