Maybe I just read some player's incorrect post, but swore I read something vaguely official about a message when settlement is being attacked - maybe won't have time to get there, but at least just to know, so you can go check up.

But either bug or the post I read wasn't correct - because my nice food farm of Abernathy Farms, with plenty of defense, was attacked while I was off somewhere, and no message.

I only found out about the attack because noticed when checking that the defense rating was looking low - lot lower than the machine guns I'd already put in. So traveled there, and turns out 2 of my heavy machine guns were knocked out of commission. And the settlers there had voice prompts which started telling me how bad it was, the attack, blah blah

Fixed the broken turrets and left, but now I'm wondering if my settlements will be attacked and I don't even know it happened.

Mainly, I want to know so I can maybe hurry over there - not so much that I can help, which would be cool. But I really want to see how and where the attacks come in, because without that info, it's hard to design defenses unless you go totally crazy or have a really obvious attack point like fortunately Sanctuary with the one bridge in. Although out of paranoia I have machine gun turrets all along the river wall too.

Hm are you sure you didnt just miss the attack notice since its just a small pop up in the top left corner of the screen, the actual quest for going to help shows in miscelanius quests after you get the pop up so its not rly that hard to miss it.