Oops! Sorry Penny me luv. I didn't know there was a new Quatermass. My vision of your youth and beauty has been fully restored.

As an engineer I have always enjoyed speculation about visitations from aliens. In the Von Daniken era I read what I could find. At first with great interest, which rapidly turned to disappointment as there was no scrap of 'evidence' of any visitation. Von Daniken had several great theories which completely broke down due to the lack of any evidence.

Where's the hardware? Where are the nuts and bolts and rivets that would have held their devices together?
Even assuming that and advanced technology may have overcome their reliance on the simple rivet, there would still be the 'bones' of their technology to be found. It would be found in the strong parts of the structure or containers of their devices. The chassis, or mother boards or corners of the cases or enclosures. Where are the food conatiners which they most likey would leave behind.

There's nothing ever been found that could be remotely ascribed to be of alien origin.

Bert.