Well thats a theory that ended in a dead end which is a good thing as it reduces the variables
I set up a new test from a generated battle using a map that was edited but not saved exactly like my earlier posts today
They are not the exact same buildings but that does not seem to matter
At set up
The targeting
So it looks like the luck of the dice didn't show it in the earlier tests but these ones do and this one and the earlier one were both done as a Generated battle that had the map edited then the bombardment targeted on the buildings so it APPEARS that the problem is not in Map saving which, I guess, is "good news" .......it's one less variable
MISSING BUILDINGS
After re-loading the save the buildings are back
WHY the earlier example that had three complete arty attacks with the same arty and didn't show a missing building is a question I hope I find the answer to but for now remains a mystery