This was the call (or non-call) that changed the game. On third-and-one, Matthew Stafford threw to tight end Brandon Pettigrew, who was covered by linebacker Anthony Hitchens. Hitchens had his back to Stafford and made no intention to look for the ball. An official threw a flag and announced a defensive pass interference penalty, but somehow, the call was reversed. The Lions punted, and the Cowboys drove down the field for the winning score. No one really knows why the flag was picked up.
The officials haven't released an explanation of why they reversed the call, and I can't really think of any precedent. A similar situation happened last season, when Luke Kuechly had his back turned to Tom Brady as he threw to Rob Gronkowski, but as Clete Blakeman explained after that game, the officials determined the ball was underthrown and would have been intercepted by the second defender anyway. There was no second defender here, Stafford's pass was accurate, and Hitchens didn't even feign an effort to locate the pass. It looked like clear pass interference. We'll have to wait for tonight's officials to clarify their decision.