I have to say: one of the most surprising and unfortunate pieces of missing media in the BBs' story (other than the Good Vibrations multitracks) has to be that there are no photos of Brian in the famous sandbox with the piano.
Right?! I completely agree. For the amount of mythos surrounding it, you'd think there would be at least some information about it. I know he kept it until he moved again (to my understanding the Steinway was in the Laurel Way house and moved with him to Bellagio), never to be seen again.
Of course, at the time, they didn't know that history was being made that would one day become the topic of dissection and conversation. Still, this would (to me) seem weird enough - even by 1966 Brian standards - to have documented by *someone* with a camera.