I'm also not sure on the "not so good a job cleaning". It sounds like they left the liver inside the body cavity? Not much cleaning from what it sounds like. People leave deer overnight before retrieving them without field dressing them quite often in those temperatures, but a moose is a much larger animal and will retain heat much longer. My conclusion would be that the spoiled meat would be directly related to the poor job field dressing or that the temperatures were much higher than 60-65 degrees.