PROVIDENCE-- Providence police and a private investigator are trying to determine what happened to a recent Brown University graduate from Russia who was reported missing.
Konstantin Salikhov is 31 years old and hasn't been seen since a trip to the West Coast last month.
Salikhov is 6 feet tall and recently completed a doctorate in math. He's an avid runner.
"Just a quiet reserved kid. Didn't need much. A minimalist. Never knew he was a Ph.D. in math," said Stephen Kariotis, Salikhov's landlord.
Salikhov has lived at 210 Waterman St. in Providence for the past five years. He left a note inside his small apartment saying he was on vacation until Aug. 24. He told his parents in Russia he was going out west on a camping trip in early August by himself.
He sent photos to his parents, whom he talked to regularly. He hiked in Sequoia National Park and visited geysers in Wyoming before returning a rented car to San Francisco on Aug. 20.
He called his parents the next day.
"I believe this because of the connection and whatever the time was, it (the phone call) was kind of broken up. He just stated, 'Mom and Dad, I'm home and I'm safe.' And that was pretty much the extent of the phone call and, 'I'll talk to you at a later time,'" said Mark Chauppetta, a private detective.
Salikhov's parents hired Chauppetta when they didn't hear from their son.
"They were pretty close-knit, kept in touch with each other. And then after not hearing back from him, that's when they became concerned and called the Russian consulate office," Chauppetta said.
Providence police said Salikhov's credit cards have not been used since Aug. 20 and that there has been no cell phone use in the past 2 weeks.
They said they believe Salikhov is still in California, but San Francisco police told NBC 10 that they know nothing about the case and that no one has contacted them.
"They probably felt that there was no crime committed, that he's a 31-year-old male. He likes to camp. He hasn't shown up. He graduated from college. So, I don't think they were that concerned," Chauppetta said. "But now, not being in touch with his parents, not being in touch with anyone, not being seen here."
The car Salikhov used in Providence is also missing. It's a silver Hyundai Elantra with Rhode Island license plate 712-678.
Officials at Logan International Airport and at T.F. Green Airport reported no sign of it.
The detective is trying to obtain records from Salikhov's checking account and to find any record if he flew back from California.
Providence police asked anyone with information about Salikhov to call them.
Brown University released a statment on Wednesday, saying Salikhov received his PhD in mathematics from Brown in May 2010.
In early September, Providence Police contacted Brown's Department of Public Safety (DPS) concerning a possible missing person investigation of Salikhov. Although Salikhov is no longer a student at Brown, DPS has been cooperating with Providence police on this matter.