I don’t know what health issues the driver might have had, but not urinating for a long period means you’re severely dehydrated (well, there’s also prostate trouble, but that’s a different matter).
I used to work in open-pit copper mines here in Arizona, where the temps at the bottom of the pit would routinely get over 120 in the summer. Heat disorders were all too common, and one of the standard safety topics was how to recognize them and what to do about them. One thing was always to drink LOTS of water (or Gatorade if you like the stuff). Another thing is that if you do suffer heat stroke, you’ll always be at increased risk afterwards.
Time for the driver to get out of the delivery truck and find a different job. Not easy at 58 but he could die next time.
He was already in kidney failure by the time they arrived.
I worked in a forging plant and it wouldn’t stop work until the the temperature reached 120 degrees we drank a lot of water and they had salt tables to prevent the body from losing minerals.
He didn’t die just because of heat.