This is a well designed app (well except for the overly busy icon), but suffers from the same problems Wikipedia on the web suffers from, which is to say a very, very poor search capability.
On the web, you can just use Google and add "wiki" to whatever you are searching for to get around the many failures of Wikipedias built-in search. Here there is no such option unfortunately.
It does that thing that Wikipedia on the web does where it assumes your search terms are for a title of a page, even though no one in their right mind is ever searching for an exact page title. So often you waste a huge amount of time trying to guess the exact title of a page that *may* exist when you should be allowed to just enter some text and have the search engine figure out the closest match.
In the app, there are actually buttons to select between searching for text and searching for page titles, but its not clear at all which of these is actually active at any given time (extremely bad graphics there). They also regularly just dont work. You can select either one and search for text, and *both* will return the "no page with that title" error, even though as you are typing you can see multiple pages coming up that actually *do* have the text you are looking for and even some with the title you are looking for.
Jeremy Bee about Articles, v2.3.1