Did you go through the entire list?
Search results are probably NOT alphabetical, if that's what you mean. Usually most popular or most clicked search results show up first.
Nah, that's not it. Search results cut off after a while. They don't return all possible matches. And yes, they return games in order of popularity, so those that don't make the cut simply aren't included. When you search for full title, exact matches are simply more relevant, so they show up on top.