I can understand why the op was down voted, but just assuming that a civilization was "not smart" simply because we cannot find evidence feels dumb.

> The real bigots are the conspiracy nuts who think ancient civilizations we know of couldn't have achieved the many things we evidence of, and think it must have been aliens

You are not presenting any evidence that it was otherwise. I am not saying that this device was presented by aliens, but neither you are that it was not.

> So should we assume they had such things? We simply make the best estimates we can and adjust when we find wonderful surprises like this one.

We have evidence that they had it. How they had it is a separate question.

I assume the next "civilization" might not be able to figure out how/what out machines are doing and they would have a similar discussion.