Authorities are investigating Bernstein's death as a homicide. An autopsy is being performed Wednesday.
Deputies had been scouring Borrego Park and nearby Whiting Ranch Park for days looking for Bernstein.
Bernstein, who was visiting with family on winter break from the University of Pennsylvania, went to the park on the night of Jan. 2 to meet an unknown person for unknown reasons, said Annee Della Donna, an attorney and friend of the family. Earlier that night he had texted a friend asking for a ride to the park in order to have the meeting, she said.
The attorney said Bernstein and the friend arrived around 10:30 p.m., and Bernstein went off alone into the park. The friend said he waited behind in the car.
The friend later said when Bernstein didn't return he sent text massages to him, according to Della Donna. The friend said he left and returned hours later to search for Bernstein.
"He didn't have anything with him," Della Donna said Friday in an interview with CBS Los Angeles. "He didn't have his glasses or his medication. He didn't bring his wallet or a phone charger. I don't think he planned on this being a long trip and he just disappeared."
In an interview with CBS Los Angeles, Bernstein's parents pointed to the left behind items as evidence that the teen planned on coming home that night.
"The fact that he didn't tell us he was going out tells us that he wasn't planning to be gone very long," said his mother, Jeanne Pepper Bernstein.
The family realized Bernstein might be missing the next morning when he missed a dentist appointment.
A cause of death remains unknown.