I think the article greatly underestimates our archaeological capabilities. We can identify five mass extinctions in the last 500 million years, so why should such a civilization simply be overlooked? Of course, we wouldn't find abandoned ruins, but the idea that an industrial civilization wouldn't leave behind any detectable artifacts is practically impossible. Perhaps there were a few primate species before that could make fire and hunt with bows and arrows, but certainly nothing industrial and hardly any extensive agricultural culture.