The largest obstacle to this theory being taken seriously is the lack of evidence in long term records, such as ice cores.

Our current age will show up in future ice cores as a massive spike; we affect CO2, Methane, Sulfates, and probably a lot more. Additionally we produce and have produced various synthetic compounds that will remain detectable in the environment for hundreds of thousands of years, if not millions.

In order to circumvent this lack of evidence such a society would have had to had a very small footprint, taken very specific industrial steps, and had a focus on research that wasn't exploited. This is highly unlikely - most of our lessons have actually been learned from exploitation, and most of our research facilities require astounding amounts of labour to construct. This isn't even touching on the social improbability of maintaining such a society.

> This is highly unlikely

Absolutely. But are visitors from other star systems any less unlikely?