So suppose this.
You are davening mussaf today, and you say all the right stuff, but then you start spacing out during v’hasienu and space back in during sim shalom. So you probably said only mekadesh hashabas. Because you were davening by heart.
So you go back to atta bchartanu, and say all the right stuff again. And then start spacing out again, but this time you are reading the siddur. So you probably said only mekadesh yisroel v’hazmanim.
So you said both brochos. So probably you are fine.