But has many different spots on the moon been tested with a laser from Earth? I predict that more such reflective spots will be found. And the spots will not appear darkened in the sunlight. The spots, such as highly reflective patches on moon rocks, will appear bright on photographs. The spots will be small and only show up on very zoomed in photographs of the moon surface. I haven't seen any such closeup photographs (not counting the Apollo studio shots).
So...the spots are very small, and only shiny at laser frequencies. All of them, Anders? You are aware that several different frequencies of laser have been bounced off the LRRR, right? Or perhaps this magical substance only shows its remarkable properties to phase-coherent light!
Hey, here's an idea. Since as you say a simple bit of applied QED can calculate if ordinary substances are capable of this behavior, let's go looking for one! I'm sure there are a lot of people who could use such a selective reflector.
Just off the top of my head, chroma-key could benefit from it -- imagine being able to selectively reflect just the LED back to camera without any ordinary light at all reflecting off the backdrop! I can imagine security applications as well. And given a moment or two, I could come up with places where they could be used in fabrication and medical use of lasers...
Why has no experiment been done to test the speed of light from a moving source relative to an observer?