I hardly think you can say that you felt mercury leaving the brain. ;) Could be a lot of things. There's no human that can actually feel the little metals moving.
But lecithin is actually good for the brain and is taken for brain and nerve health. I believe it helps with the myelin and linings of the neurons. So that might be what you were feeling. But who knows, maybe it does chelate the brain, I dont know. My guess is that it doesnt.