Couldn't he check the fourth finger of her left hand, to see if she's wearing a ring?
Some of us are socially inept and fail to notice the obvious.
I know quite a few married couples that do not wear rings these days, and for a wide variety of reasons. Some don't like jewelry at all, others do not see the point (it is, admittedly, little more than ritual), and others have jobs or medical conditions which prevent them from wearing the rings (my father has a bad reaction to gold, as a real-world example). In other words, it is not a very reliable indicator in the modern world, doubly so since there are single women that wear apparent wedding/engagement rings.