"Although there is only a tiny probability that alien technology would have left traces on the moon in the form of an artefact or surface modification of lunar features, this location has the virtue of being close, and of preserving traces for an immense duration."
So far, an examination of the NASA images has located the various probes, rovers, and other debris left behind by American and Soviet space missions. Not a trace of extraterrestrial intervention has been found.
I would think that if ancient aliens came all the way to earth, they would be more likely to set up shop down here with all the water, resources, and warmth. But that's just me. For all I know, aliens like bone-dry deserts with neither water nor air.