When looking at the security footage, the remark is made that the footage is recorded over every 72 hours and that they "missed the loop" and only have up to 6pm on the day Ms. Sacks disappeared. If the footage was recorded over, the only footage available would be AFTER 6pm, not "up to", it's the earlier footage that would've been recorded over.
After the murder has been solved, Hailey takes Fincher to the taco truck he's been looking for the whole movie. The truck's website is www.tacotruck.ca, which shows that they are filming in Canada, not the US.
Hailey and the detective trace the victim's cell phone and upon entering the container do not notice any odor from the body that had been there several days. They talk about the phone Hailey finds before eventually uncovering the body. Hailey even comments later about decomposition, so despite the fact the weather was cooler the decomposition would have been very noticeable.