I would bet there's nothing to find on the ground. It looks like it vaporized in the atmosphere, like all but the biggest meteoroids do before they have a chance to hit the ground.

Only someone utterly unfamiliar with the working methods of illustrators would think this was news. Illustration is an all's-fair affair. You do what you have to in order to get the image you're looking for, including using photo references. And it's never said that Rockwell "traced" the images. He scaled them up, using a grid, as artists have done since the Renaissance.