Pettigrew had a handful of facemask and pushed off prior to Hitchens making contact with him. Also, the ball was severely underthrown. Probably should've been offsetting penalties (facemask and PI) but it didn't work out that way for Detroit. They had their share of the breaks as well like the unbelievable call against T Williams for offensive PI in the first half and the EXTREMELY soft running into the kicker call that kept a Detroit touchdown drive alive.
It comes down to this. Losers whine about calls. Winners move on to round two. Detroit had every opportunity after that penalty to keep the game in their hands. They didn't. Losers find others to blame when they wet the bed.