Notice how the bottom part is reflecting, and as we move up the handle it abruptly stops. There is definitely something to reflect, It might be a glitch in the render engine...
It looks like it's reflecting the handle and bottom side of the cup. So yeah I still don't think there's anything else for it to reflect.
But I don't know the whole science behind reflections and how they work so I don't know. Again, just an idea.
