When you look back across the history of art, things go missing. Interesting things. For example, it seems ancient people didn't have a word to describe the color of the sky. The "b" word-blue? They didn't use it. That’s the argument, anyway...... It wasn't until much later, when blue paints were invented (which happened in Egypt), that "blue" became a descriptor—when you could buy or sell it..... The Newest Missing Thing That was our guess. And now-ta-da-I've got another one, a second thing that ancients saw all the time but failed to describe. And this one is even more basic....