I too had problems finding N7 in stores, but not because nobody stocked them. Instead what I found was signs indicating that "we are completely sold out, leave us your name and number." It happened repeatedly at local stores like Best Buy, Staples, or anywhere else that kept a stock of tablets. Even Google themselves were temporarily out when I first went to purchase one, and I ended up waiting about a week or two before they came available again.
Also, as others have mentioned, I actually see them in the wild. I speak to people and they have heard of it. It has name recognition, which is something that other Android tablets tended to lack. Numbers or no, it's hard to ignore what I've seen face-to-face in the past month.