Short answer is that the creator has added a layer of checkerboard pattern on a separate layer behing everything so that the objects and any effects applied to them will show up. This is confusing to people because tradiotionally, a checkerboard pattern (e.g, in Photoshop) is a method to show transparency. If you look at the Layers palette in your stock art, you will likely see this layer and can delete it (or turn it off).
Did you truly get vector art or is it a graphic image? If it is a vector, then you should be able to find the checkerboard somewhere in the layers panel or it might be that the transparency grid has been turned on (although that is not what it looks like), which can be changed under the View>Hide(Show) Transparency Grid.