You're probably right. He most likely always used a card for everything, and if a check was ever necessary either his parents or wife happened to be the one to take care of it. But on the other hand, you would think even just
receiving a check for deposit would kind of clue someone in on how a check gets filled out. Even now, I still occasionally receive a check in the mail.
Just thinking... his mind would probably explode if he ever saw one of those old-fashioned credit card "manual imprinter" machines, in action, with the carbon paper and all that.