Hope I caught this in time...Meat processors jump through major hoops to maintain a Sanitary environment. This is why Vac-Pac meat stays fresh in the refer a couple weeks and Store Wrapped meat stinks in 3 days! STORE BUTCHERS are the Number One cause of Bacteria on Meat!
That mass of meat was Cold, a large portion of those hours. While Bacteria " can " grow at 50°F it take a lot longer than 12 hours to reach dangerous levels. Any Bacteria are Only on the Surface and the majority of them or any toxin can be washed away, especially with Vinegar or Citrus Juice, being Extra Careful, not to contaminate other items near the sink. Additionally, the Toxin that causes Botulism, is destroyed after a few minutes at 185°F. This is another reason we Smoke at 225.
Putrification/ Spoilage Bacteria are NOT harmful, they just make meat stink. They too, do not grow fast at 50°F, but are more noticeable. The Nose Knows!
If opened Today and it smells fine, is washed with White Vinegar and water rinsed, dried, covered with a Salty Rub, Wrapped until the weekend and Smoked at 225+, there would be no issue.
Do what you are comfortable with...JJ