I recently went to Vinne's airstream repair and had Bryan do a ceramic coating. I too had a scratch from a limb that Bryan thought he could get buff out before applying the coating. It also did not go through the clearcoat plastic. He has to clean the trailer completely or he will seal in the dirt. He could not buff the scratch no matter what he tried. It looks better maybe because the coating helped a bit, but it is still there.
Other than replacing the panel,
I think you will have to live with it.