Quote from rmorse:
In front of you? Vix markets are a single list. I don't know how your "smart" order is routed. Most likely directed to a dark pool, then the floor. It's hard for me to guess if the market moved or the market makers faded from other factors. It's hard for me to believe that a dark pool participate would go from offering in the dark pool to taking the offer in front of you. It's is possible they faded their offer on the CBOE book, after making a sale to you.
A lot of market makers size on the book is larger than they want to play, to get a larger percentage of a trade. If your order was directed to the CBOE, and not a dark pool, and the market was moving, you would have had a better chance of sweeping the book, IMO.