Quote from winter:
So my question is this, how do traders prepare or plan for such a worst-case scenario? It doesn't sound like my losses are bounded by any real amount - how does a prudent money management plan take a "once per decade event" into account?
Make sure that you have the ability to trade multiple markets and make sure that you will be alerted to an adverse event if you have trades on when you are not monitoring the market. Be familiar with other trading markets so that you will know what is the appropriate hedge for any possible event.