In the situation described, it sounds like he needed to bring along vaccines that would have to be refrigerated. I wouldn’t normally use my keys to remember something, but if the only time I used them was when I put them in the refrigerator, it might theoretically be okay, except for the thing I mention in the next paragraph. Definitely less crazy than me putting my shoes in the fridge.
But the other thing is that I’m personally a bit paranoid about losing my keys, or having somebody take them, and can’t ever leave my keys in a public area of the house. I might actually have to put my shoes in the fridge like a crazy person.