This is VERY fishy.
#1 - Since when is having a deer in the back of a truck poaching? Was there an out-of-season date on the photo, did they include text indicating it was poached, or what? Plenty of deer in the back of trucks in posts here with no black helicopters showing up.
#2 - I grew up in MI (this is where it occurred, right). While I have little respect for the DNR there based on my experiences and those of other acquaintances, unless laws have changed it is not illegal to have meat over one year old in your freezer, nor are you required to keep the tag once the carcass is processed. How would they tell what meat when with what tag anyways?? The processor I used regularly had a DNR officer there aging/measuring deer and sent me out the door past them with bags of meat, and no tag returned with it.
#3 - Monitoring an entire neighborhood's phones, blocking the street, going through everyone's freezers? Now the DNR has a little more investigatory discretion than the police but they still have to have cause to get phone taps etc and what you describe is beyond reasonable belief.
While I have serious doubts as to the truthfulness of this story, I have ZERO doubts that people don't understand the risk they put themselves at when they post stories about illegal hunting practices or pictures showing evidence of illegal activity. A couple years ago I saw a post by a guy where he shot 2 bucks in Montana -- illegal, and the authorities were contacted though I did not hear the outcome. In another case, same forum, some people posted pics of picking up winter kill sheep heads. The landscape was recognized as somewhere they were not supposed to be, and the authorities ended up getting them on multiple infractions. Finally, I have a buddy who posted a photo that was taken out of context and he while he was cleared of all suspicion he had to endure a very uncomfortable investigation.
Moral of the story: Don't break the law. Assuming you are anonymous on the internet is also a bad idea.