I placed a limit order yesterday for (negative) 18% of the stock's closing price and it got filled.
The $5 sell was probably an institution dumping shares coupled with a super low bid put in by a smart investor. I've done it a couple times. You basically put in a bid for a very low price and cross your fingers hoping it will get filled. Sometimes the bigger institutions will just drop all their shares at once and fill your bid. It's very nice when you get filled.
I am actually surprised the stock was hit that hard and my bid got filled. I'm up even more on this stock.