The area itself makes no sense to be stooging around at apparently low level in broad daylight in an unusual aircraft with a chase plane. Why Calvine? Somewhere in the area of Spadeadam might have made some sort of sense
Machrihanish is mentioned but I do not see why. There seem to be no reports of odd looking aircraft though Campbeltown is close by.
There is no mention of any other sightings on that day from anywhere else or by anyone else. If a thing really was that odd, surely there should be other sighting reports of it in transit?