I think situational awareness and firearm readiness helped avoid a bad situation. I also think "Bob" needs a credit card, but that's probably not going to happen.
Good job for situational awareness and being armed. I love that! BUT!!!!
There are many things that cause me to be what is known as a "Luddite". You can look that up. Not carrying credit cards is not one of them.
Not carrying a credit card is an old man's obsession with privacy, or his fright with respect to identity theft, or fear of Big Brother and the Feds, or just being old fashioned to the extreme, or all of the above. In the 21st century it's a stupid methodology to try to pretend you're off the grid. Ain't nobody off the grid unless you live in a cabin in the woods and hunt and fish and grow your own crops and have some kind of generator, etc., etc., etc. No phone, no recognized home address, and the car is in his wife's name, I suppose. So she's on the grid, he's not, yippee, good for him.
One presumes that at age 78 he has refused Medicare and Social Security, too. He got paid in cash or kind his whole life and nobody has a clue who he is, where he goes, what he does, etc. Oh, and his home is only in his wife's name.
And he hasn't purchased a firearm since before 1968.

I guess his $100 bill came from his wife's bank account.

It gives Luddite new meaning.