Not an attack on your post BOAC (difficult to express intonation in text!), simply pointing out there's a lot of stuff that'll bring an airliner down before VA does.
I have seen no evidence of VA damage. I know of no other engineer that has. Friends of mine work in engine bays as well as line stations, the grapevine would quickly flash up evidence of this nature, if it didn't Sunfish would!
You're right, I have no record of birdstrikes at FL400. Nor have I any evidence of volcanic ash damage.