The way the Winchesters parked looks like they came in driving towards the intersection. But that is impossible given the fact that it is a dead end. Even if they did reverse in, they still would have seen the crime scene coming in. Plus, the police are still putting up the crime scene wrap several hours in.
The goof item below may give away important plot points.
During the last fight between Sam and the Skinwalker at Rebecca's place, the Skinwalker puts a knife on the pool table. When Sam flips up to cut his hands free, we see that he has bound feet. In the next shot, his feet are free already, without him ever having a chance to use the knife to cut the rope.
Towards the end of the episode, right after Sam cuts the rope binding his hand and kicks the shape shifter "Dean", Sam wields the knife. "Dean" grabs his arm and flips him upside down and the knife disappears: it's no longer in Sam's hand and not on the floor.