Corliss pointed out years ago that many of the claimed OOPARTs “found” in the geological record might be remnants of ETI expeditions to Earth, or fallen space-junk. And Chris Boyce, before his death, wrote this interesting little piece about the VNPs from ETIs in our solar system…

That said, elements within the vN presence would probably be capable of fabricating somas, near perfect artificial likenesses of biological forms, for their own purposes. Possessing arbitrarily advanced technologies which would appear indistinguishable from magic, they could represent themselves to us in any manner they wished. That said, it is important to bear something in mind: should vN choose to expose humans to their artefacts whether somas or whatever, their motives in doing so are not likely to be clear to us.

As things stand we have no evidence of contact between humanity and vN. Logic does dictate that if ET societies exist vN are virtually certain to be in the Solar System, perhaps with a presence here on Earth or close by. In this event they are leaving it up to us to find them and make up our own minds as to whether or not we wish to knock on their door.

…from http://web.archive.org/web/20010308105914/www.et-presence.ndirect.co.uk/Articles/vN/logical_contact7.htm