Oh, this literally happened yesterday.

Someone sold off 5k bitcoins (~USD $450k at the time).

That's exactly what happened. Big sell off from 95 to 80ish, and then it sprang back to ~$90 today.

There's low confidence in it right now, but that's because most players are actual players. They aren't using bitcoins for groceries, like a bank reserve (yet). They're playing them like stocks.