I believe this as I've seen dogs visibly freak the fuck out when they think a human they love (or in the case of some dogs, a human that just exists. Because they're all good boys and girls) is in danger.
I tripped and fell over one time and the racket I made woke my dog up. He looked across at me lying on the floor, yawned and went back to sleep. "Still alive? Jolly good. Wake me again at dinnertime."
Lol my childhood dog was like that... However, I have no doubt that if there was any real danger, she would have known immediately and been right there.