A 28-year-old doctoral student from Chicago has gone missing while hiking in Costa Rica and his parents, a Highland Park couple, have gone to the Central American country to search for him, a family friend said today.

David Gimelfarb was last seen Aug. 11 at about 10 a.m. by a park ranger as he drove a rented sport-utility vehicle in the Parque Nacional Rincon de la Vieja, a national park in the northwest part of the country, according to the friend, Michael Kipnis, and a Costa Rican police report he provided.

After not hearing from their son for two days, Gimelfarb's parents, Roma and Luda Gimelfarb, flew to Costa Rica and are still there, Kipnis said.

"He [Roma] was OK," Kipnis said of his last conversation with his friends, who called from their hotel in Costa Rica. "She's not holding up very well."

David Gimelfarb is a doctoral student studying psychology at the Adler School of Professional Psychology and lives on the North Side's Buena Park neighborhood, Kipnis said. He graduated from Highland Park High School and earned an undergraduate degree from Beloit College in Wisconsin.

He left about a week ago to hike in Costa Rica, Kipnis said. He is close to his parents and called home almost every day.

According to a Costa Rican police report filed by his father, David Gimelfarb was staying at the Hotel Guachipelin in Guanacaste province. Roma Gimelfarb tried calling his son at the hotel on Aug. 12, but he couldn't reach him. The hotel told him his son left a day before for the national park and had not returned. Repeated calls yielded no more information, according to the police report.

Worried, the parents traveled to Costa Rica on Thursday. When they arrived, they learned that there was already a search party from the local Red Cross in the park searching for their son. Their son, the group said, went to the park alone for a hike. His rental vehicle, a 2009 Hyundai Tucson, was found in the park. It was locked, according to the police report.

Rain, dense forest and the size of the park, which according to several sources is about 55 square miles, have slowed the search. Gimelfarb's parents have sought help from officials at the American embassy in San Jose, the Costa Rican capital, but have been disappointed with what they believe is a slow response, Kipnis said.

"They were told: 'There is not much we can do. Thank you very much,' " Kipnis said.

A U.S. Marine sergeant who answered the phone at the U.S. embassy confirmed that Gimelfarb's mother had called regarding her son. The marine said no one was available to release information on the search.

Attempts to reach Roma and Luda Gimelfarb in Costa Rica were unsuccessful.

Kipnis said he has known the Gimelfarbs since he immigrated from Russia 30 years ago. They had come to the United States about three years before. He said David is their only child.

(The Chicago Tribune contributed to this story)

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