This aspect of BTC specifically makes me roar with laughter. The fact that anyone is willing to hope that Nakamoto's coins are "lost", discounting their very real value should he/she be sitting on that cash cow. What a great con on their part. You say trading of those coins will be noticed "immediately". The transaction log will cement that trade before (well, as) it's noticed. The only thing people will notice is the aftermath. Those who are personally monitoring the blockchain with automation will notify themselves within 5 minutes, while the public at large won't figure it out for hours. By the time the "BTC is now worthless" headlines hit the major news outlets, it will be too late for the average user to cash out.