Technically the plane was not hit directly.
It disintegrated from the shockwave of a missile detonating close by...............
That’s “shot down”. If the explosion causes structural damage that makes the plane come apart....
I recall reading what might have been a declassified document that the reason he was in missile was due to the then-top-secret vulnerability of the U2’s turbofan engine: Flameout at high altitudes.
I can’t find what I was looking for, but this article elaborates on the problem.
Even a torpedo isn't actually striking a ship, although nobody denies the torpedo sank the ship.