So the water jug doesn't last multiple days? or Even one 24 hour cycle?
Opinion only------
I noticed your signature says you are in Maryland, the temperatures are much more moderate there than in many of the locals the rest of us are posting. Here S. La. 95-100*, with 100% humidity = 105-110* heat index.
Was/is the chicken caged in direct sunlight?
Sadly I have to say that in all the years I have raised chickens I have had a couple of occurances in the summer where my chickens ran out of water, at one time maybe 24 hours. Bright sunshine, extreme heat, 100+ heat index. And I lost not one. They were able to retreat into the shade, lay down conserve energy, and survive. They were very thirsty when I did give them water, and if it would have went on another day I am sure I would have lost some chickens.
Point is--- even with my extreme heat conditions here, while not healthy, they made it through the daylight hours (12hours), for one day.
I think that chicken either had some outstanding health issues that weakened it or it was out of water for more than one 12 hour daylight/heat cycle.
Now I have auto water, 5 gallon bucket with a water trough float in it, along with 2 secondary gravity waterers. Even if I lost water service, my chickens would have water for up to 72 hours. 3 days. In that time I would be able either to restore water service, or begin hauling water filling gravity waterers, or recruit some one to do it if I were physically unable to do it myself.
When was the previous fill of the waterers prior to your husband's fill? Just saying that it sounds to me like that chicken went more than the period of time described without water.
