The journalist should've figured out that Amy Klobuchar was a senator and went from there in further doing his homework.
On the other hand, even people who can name all one hundred senators might not be able to recognize them all by face.
I can't identify all by face (I don't remember what John Barrasso or Dan Sullivan or Jim Risch look like, for example) but I think I can identify all the women because there are unfortunately so few of them.
Even when I saw Ed Markey, my own Senator, I wasn't 100% sure it was him until I heard someone say it was. That's the only Senator I've met in person.