Very Good Job. Now..... what *exactly* was the payload, knowing what we know now?
If that is LOX venting for cryogenic cooling it could probably be ignited in conjunction with the AlLi alloy skin with a drone and an off the shelf laser.
I cant really see the passing craft having fired something because the recoil would have altered the path of flight more, unless its a pretty beefy autonomous vehicle.
If it had released something that subsequently engaged its own propulsion I think wed have readily seen that and the impact would have been more in line with the object in flights passing.
Another possibility is that the passing object illuminated the vehicle for a lock by a Tracking Point type scope at extreme range and someone put a bullet into it from 2000+ yards. IDK if the actual Tracking Point can work like that, or if theres a mod or a different one that can do it.