[sametmax]

The mp3 player itselft won't last 55 milions years. It will break way before. And be buried in the sand by the first sand storm, no matter how flotty the sphere is. Footballs get buried in the desert, no matter how light they are. Source: I lived in Bamako.

[ajuc]

I think if it moved a little every so often it would get unburied. But I don't live near a desert so maybe I'm wrong.

[sametmax]

You will have so many sand storms in 55 millions of years. And one is enough.