I looked on the Wii online store under WiiWare titles and it told me AC: City Folk was one of them. I went to my console and searched for it, but to no avail. I even tried looking by genre and it still didn't show up. Little dissapointed that I can't download it as none of the stores around here have it.
Animal Crossing: City Folk is not a downloadable game. It is available as a disc in a physical package. Here is information about the game from Nintendo: http://animal-crossing.com/cityfolk/
Are you sure that the Wii online store said that AC: City Folk was under WiiWare titles? I doubt that it would be under that category becuase physical games are not called WiiWare. Perhaps you were reading about the additional downloadable online content that is available for the game. More information about that content is right here: http://animal-crossing.com/cityfolk/connected/
Also, you can find the game on Amazon or at a large retailer (if you are in America) listed here: http://www.nintendo.com/consumer/retail/retail_retailers_product.jsp?itemid=CyRXNiuwtxm0AgyMbOyehZ7N5f4JwIPy&title=Animal+Crossing:+City+Folk&platform=Wii