Look at it this way. When you look at the object being reflected, it is as if you were looking through the reflecting medium to see the object. The reflecting medium is "transparent". You know it's there but the camera doesn't. The camera "sees" the reflected image the same as if it were viewing the object directly.
Play around with this. It is a difficult concept to grasp. Leave your camera in auto or program mode and select manual focus. Focus on the reflecting medium. Is the reflected image still sharp? It shouldn't be. Now, focus on the object. Is the reflecting medium sharp? It shouldn't be.
The reflected image doesn't exist at the reflecting medium. It exists in the camera or in your eyes. The light rays coming from the object are bouncing off the mirror or glass and entering your eyes.
I hope this helps. If not, I need help!
Think about this. If you are shooting a DSLR, when you look through the viewfinder, the image you see is being reflected first off a mirror and then three or four times from the surfaces of a special prism. However, you can't see the reflecting media inside the camera--only the image.