In the world of art, an artist's name can be used to refer to his works. Not too long ago, the Chicago Tribune ran a piece entitled "Unknown Van Gogh Pops Up In Wisconsin". It was about a painting, not one of Vincent's distant cousins.
Originally Posted by Gerald C Koch
Since the exhibit has several photos, it could have been called Unknown Weegees. On the other hand, perhaps the name is intended to refer to the artist, in the sense that the photos give us new insights into Weegee himself. An example of that approach is seen in a biography of Abraham Lincoln entitled "The Unknown Lincoln".