Well, it still goes back to the fact that it won't work if they freeze. That is the one condition that can't happen. I don't know why they would have froze when the dog's water did not, but they froze so something was up in the garage that allowed them to freeze solid. I suspect something to do with being sealed in an insulated box that insulated them from what heat there was.
For it to work it cannot freeze. Nice and cold is good, but not freezing.
As for storing in the fridge. I was not referring to a non-working fridge, but a working one. In that particular case the person used an old working fridge just like a root cellar to keep the plants cold. He just set the temp lower, bagged the plants and stuck them in the fridge.
Bart