Looking in the wrong places

There is an old story about a policeman coming upon a drunk crawling under a stretchlight. The policeman asks the man what he is doing and he replies in a slur, "I lost my keys and I'm looking for them." The policeman decides to help the man. However, when, after quite a bit of searching, they still haven't found the keys, the policeman says, "Wait. Let's retrace your movements when you lost the keys. Where exactly were you when you dropped them?" The drunk pointed across the street to a dark corner. The policemnan, frustrated, rebuked him, "Why weren't you looking over there for them, then?" The drunk replied, "Cause there's more light over here."