It was a whole muscle. There were no nasty bits inside the meat. They would have been on the outside, and the cook temps were over 200 degrees. All the nasties were long dead.
There was a probe inserted into the meat at least 1 time. When and how many times was it probed during the 8 hours it took to get to 135*F.
Was it injected before the cook? All of that poking could have put the "nasties" inside.
How hot was the cook during the 8 hours? Did it drop way low for awhile?
Nasties grow between 40*F and 140*F
Be safe, a cheap piece of meat is not worth getting sick or death in rare situations.