When Jessi attacked Lori after the party, the party had come to an end and Lori was taking out the garbage. Now, when Lori and Declan see Jessi on tape with Lori's necklace, they are at the party. This makes no sense. Even if the party wasn't over, Lori wouldn't have gone back in to dance after being attacked, and it's doubtful that Jessi would have gone back in while carrying Lori's necklace.