The interesting thing to me — if the incident actually happened — why could the alien craft not detect (or fail to detect) the absence of nuclear material if their technology is so advanced otherwise? Heck, we can do that if it isn’t shielded too well.
The claim of folks who study this stuff (and don’t debunk it) is that the aliens have been trying to convince humans (in the US, the then Soviet Union and elsewhere) to stop developing and deploying nuclear weapons.
Again according to their claims there are two main reasons the aliens care about this:
1. Many are not from “outer space” at all but in fact live with us on this planet (though hidden in various locations) and would not like to see their planet turned into a radioactive mess.
2. Many are from “other dimensions” (whatever that means—lol) that are disrupted by nuclear explosions in ways humans do not understand.
I’d guess their objective had to do with the missile and not the simulated warhead.