If the A invests $1000 in bitcoin, then the next day the price of bitcoin drops dramatically and the A loses $1000, which makes me curious, where does the $1000 A money go?
That is how everything works here so, apart change in the real life changes is normal aswell in the marketplace where the charts got red and green.
Now. Where does it go ? In your wallet
It just stays there it never been stolen just been deducted or increases due to corrections in the process of the investors movements and idea which they trade, sell, hold and buy.