If you are a high roller, you should seriously consider moving some fiat to btc-e just to leave some ridic lowball orders out there, it might be a huge +ev move in the long run.
Like when btc dropped to $102 in Feb because some guy hit the sell button instead of buy.
Yes, how the hell do you not check 50 times when it's with these kind of amounts? :|
It was probably a cascading effect caused by a large margin call, nothing you can do about that except not trading on margin. Not that uncommon to see this on btc-e (also happened once on bitfinex) because of their shallow orderbooks and the margin trading there.