Because I'm unfamiliar with your H's "norm" I'm just curious about the potential simple reasoning:
Is it possible that he misplaced his "regular" credit card, and used the joint one instead? It sounds like this is unlikely because perhaps he'd have alerted you if this was true. Or is it perhaps possible that he legitmately just pulled out the wrong card? I always keep certain cards in certain slots in my wallet. If I accidently swapped them I wouldn't notice if I used the wrong one because I move by habit.
You of course know him best, so you and Job are likely correct in this is some possible button-pushing.
BTW, I LOVED your first paragraph because it's just so accurate. I'm going to copy and paste it for when I'm wondering why things aren't staying the same. It's a reminder I need to expect change at every turn, and not sweat it.
