I had the same issue with it not showing up. Worked around it by doing a Google search. The first link on search results, after "scholarly articles", is the iTunes link for the app. I can only assume that there is some glitch in how the search tags are linked from within the App Store.
Thanks, it seems with some service, it simply will not show the app unless you are on wifi, as some sort of protection from people sucking too much bandwidth. Verizon actually suggested I download it on my PC thru the itunes store and install it that way (hate to say this, but don't have a clue as to how to do that).