I had a young hen this age die suddenly a few years ago. I cut into her and found several "hard boiled" eggs in her abdominal cavity, indicating she had died of internal laying. It's not know exactly what causes it, but the eggs progress a ways down the oviduct, but before getting to the shell gland, they reverse course and go back up and spill out of the oviduct and into the abdomen, accumulating there. If that's what happened in your hen's case, there will be no mistaking what your husband finds.