El Grifo,
Here are a couple of puzzling questions:
If the guy who came to you in your shop was an American having served in the USAAF during WW2 and NOT in the RAF, then his "Spitfire story" is nonsense - right?
Consequently he would be unable to find the field used for his alleged forced landing during WW2 - logical conclusion!
So, I wonder which objects in the Scottish countryside he would have asked you to photograph for him - have you thought about this?