At :57, Jenna throws the knife into the neck of Dalton's man. After finishing him, she takes off without the knife in her hand. Her next scene, she confronts McNamara and she has the knife.
In the second scene of the film when Jenna (Kristy Swanson) is about to assassinate Jordan (David Dukes) on the beach, the left-handed Swanson holds the Steyr AUG rifle, which is shown to be designed for a right-handed shooter, however. Odd since the AUG is world famous for its ability to be set for a right- or left-handed shooter.