The short video showed people speculating who put the piano there but I prefer to think it's the piano from the story. It's travelled around the world on the ocean currents and it's tired, it wants to settle down, it wants to be rescued from the sand bank, restored, and to return to a family home. I'm almost tempted to reclaim it myself...if not in reality, in a sequel to the original story.
But we all know most sequels are no good. If only the writer of the original were still with us...