You just have to remember that the reflection is actually seeing the (reflected) object from a whole different point in space. You can test this in a 3D scene by "mirroring" the camera, place it where the reflection would see the object from (see attached image, if the top camera is your regular camera, the lower camera is "what would be seen from the direction of reflection), then just hide the shelf so it doesn't block the view, and you will see that your object shows a bright highlight when viewed from that different location. You shouldn't need to get it mathematically exact for placing your "see things from the point of view of the reflection" to grasp what is going on, so don't fret about mirroring the camera location exactly.
