Quote from bln:
Maybe it was direct routed orders to another exchange than your order was placed.
If if your sell is at ISLAND at 3.90 and ask is 3.92 at NYSE and the buyer direct routes his order to NYSE your order located at ISLAND wont be filled, right?
Incorrect. Reg NMS stipulates that the NYSE route the order to NASDAQ (ISLAND? It's 2011!).