Bitcoinity.com/Markets has a giant "DON'T PANIC" image on their page. Gox, Bitstamp, and BTC-e (the websites you'd need to go through to panic sell your Bitcoin) still price in Bitcoin, so the notion that somebody would not realize something is up is a bit silly.
What website do you believe caused mass chaos?
Bitcoinity didn't have the "DON'T PANIC" message from the beginning of the switch. It was added about 1 hour later when the panic was already in full progress.