''Could it be that 300 million years ago - someone paid us a little visit? ''
It's possible but seems unlikely. Unlikely, because if it had happened, an advanced culture capable of interstellar travel, would be unlikely to be using nuts and bolts and microchips just like 2oth century human technology....amongst a whole raft of other unlikelihoods.
We for example have no hope of achieving interstellar travel in the foreseeable future, and by the time we do, if we do, the days of nuts and bolts and silicon chips will be long gone. More like nano tech construction manipulating fundamental particles....
