Yes, I remember the international events from this time well. I was only 19 but followed the news closely.
I know that 60 years have now passed since this event but wonder whether you, Stan, might be able to pinpoint the house and garden in question where the ‘fall’ occurred. Perhaps the current occupants might know something. Maybe the ‘rock’ is still there.
I know that people move around, buildings get demolished and rebuilt and all sorts of changes occur. But some things also stay the same. For example When I married in 1967 we had a house built but moved to our present (new) house in 1974 and have stayed here ever since. So if something had fallen here since then, we would have a very good chance of finding it… subject to some gardening etc. Our original house also remains effectively the same.
So, I know it is easy to remove a quarter brick sized rock, but maybe it wasn’t moved… I am suggesting that maybe a few enquiries might turn up something and suggest an inspection of the site…. A few further enquiries might be able to put it to rest one way or another. At the moment it is a tantalising question mark- what happened to the steaming dull black rock?