... if there had been a high-tech civilization on this planet, or on Mars, 200 million years ago.
Using a conservative erosion rate of 5 millimeters per millenium (in the ballpark for rock surfaces exposed in dry desert conditions where most weathering is due to sun and wind action), one can estimate what would happen to even the most gigantic structures over geological time scales.
For example, at that rate a cubic mile of solid rock sitting in the desert would just completely crumble away to dust and blow away in the wind in 325 million years, even if no other events intervened to hasten the process. This would happen much faster in a moist climate with running water, freeze-thaw cycles, and plant life--perhaps up to a thousand times faster, because erosion rates in mm./year do occur in some non-arid environments.
Artificial structures, even gigantic structures produced by advanced civilizations surpassing our own, would be far less durable than a block of stone a mile on a side. A vast concrete dam 500 feet thick would likely be completely gone in 30 million years or less. Mega-scale buildings with walls 50 feet thick would vanish without a trace in 3 million years.
Given the above, even if there had been a vast thriving high-tech civilization 20 million years ago, we'd find nothing unless artifacts or fragments were buried and fossilized before weathering could destroy them, and those items would be buried so deeply now that our chances of running into them would be remote.
For all we know, the red iron oxide dust that covers Mars is all that remains of ancient steel structures that once stood there.