A retired U.S. Army veteran is still piecing together the disappearance of his geologist son years after he vanished from an Arizona work site, with new investigators looking to break open the four-year-long cold case using new forensic evidence.24-year-old Daniel Robinson vanished after leaving work at around 9 a.m. on June 23, 2021, according to the Buckeye Police Department. Daniels father, David Robinson, subsequently reported him missing later that day after his coworkers reached out to tell his family Daniel did not return to work."When I first called in, [authorities] made me hang the phone up, wait two hours and call back," the elder Robinson told Fox News Digital.ARMY VET SAYS NEW EVIDENCE SUGGESTS FOUL PLAY IN UNSOLVED DISAPPEARANCE OF SCIENTIST SONAfter local law enforcement reportedly denied Robinsons request to begin searching for his son due to his age, the father took matters into his own hands by driving from his home in Columbia, South Carolina, to where Daniel had been seen last, 2,000 miles away in Arizona."I kind of lost it," Robinson said. "That prompted me to grab everything I could, throw it in my car and start driving to go find Daniel myself."Upon arriving in Arizona, Robinson grew frustrated with the reported lack of urgency from officials, ultimately choosing to hire a private investigator to help search for Daniel.Less than one month later, Daniels 2017 Jeep Renegade was found rolled on its side in a ravine by a local rancher. The vehicle was still in drive, and had front-end impact damage and a broken drivers side window and was missing a piece of its roof.FATHERS PURSUIT FOR MISSING DAUGHTER HEATS UP WITH NEW EVIDENCE IN CASE THATS NO LONGER COLDDespite the damage, authorities ruled out foul play in Daniels disappearance."Law enforcement gave me an idea of what they said happened at that scene," Robinson said. "It was unacceptable to me. It didn't make sense."Robinsons private investigator determined that the damage to Daniels vehicle did not match the nearby terrain, while also pointing to black box data indicating the car had driven 11 miles after the airbags had been deployed, signifying that the car may have been planted at the location where it was found."So all of the information plus more signified to my investigator that some type of foul play happened," Robinson said.AMERICAN TOURIST VANISHES IN TROPICAL PARADISE AFTER EARLY MORNING WALK FROM VACATION RENTALAs Robinson continued the frantic search for his son, local law enforcement tried to provide explanations for where he may have gone, further frustrating the father as Daniel remained missing."When [police] said, Hey, your son joined the monastery and became a monk, I had to go look for monasteries," Robinson told Fox News Digital. "Can you imagine that? I had to go and check that out. [It was] a waste of a lot of money, a lot of energy."The case remains open within the Buckeye Police Department as authorities continue to look at evidence regarding Daniels disappearance."Buckeye police are committed to locating Daniel Robinson and getting answers for his loved ones and the many people who have become deeply invested in his case," the department said in a statement to Fox News Digital. "Detectives continue to investigate every tip and lead and urge anyone with information on Daniels whereabouts tocontact us."DETECTIVES TRUE CRIME PODCAST HELPS DIG UP BREAKTHROUGH IN CASE THAT HAUNTED FAMILY: DREW AUDIBLE GASPFour years later, Robinson hopes the introduction of new Buckeye Police Department detectives and police chief will yield more promising results in finding out what happened to his son, after what had been a rocky relationship between the father and local law enforcement."Its given me the opportunity to get new leads in Daniels case," Robinson said. "Hopefully thats what well find. Because I know forensic work will bring on some new answers, and we can go forward in another direction to find out exactly what happened to my family."Robinson hopes new forensics data from the clothing and vehicle found at the scene will help piece together his sons final moments. But in the meantime he is still searching on foot for clues in the desert.MISSING CALIFORNIA MOMS FAMILY DIGS FOR HOMICIDE COVER-UP OR CLEANUP AS POLICE EYE PERSONS OF INTEREST"Me and the volunteers that come out, they are my extended family," Robinson said. "Were actually looking for Daniel."Throughout their efforts, Robinson and his team of volunteers have recovered seven sets of human remains to ultimately bring closure to other families with missing loved ones within the area, but his primary mission remains finding Daniel.In April, Robinson teamed up with another father who understands the pain of losing a child all too well: Joseph Petito.Petitos daughter, Gabby Petito, went missing just a few weeks after Daniel while on a cross-country road trip with her fianc, Brian Laundrie. Her body was subsequently discovered in Wyoming on September 19, 2021. Investigators ruled her death a homicide, determining she had been strangled to death.GABBY PETITO TOLD HER EX SHE WAS SCARED TO LEAVE BRIAN LAUNDRIE BUT WANTED TO, JUST BEFORE MURDER: NEW DOCWhen the story regarding Gabbys disappearance first made national headlines, it "pulled Daniels case along with it," according to Robinson."The first thing Im thinking is that somebodys family is going through exactly what I am," Robinson said. "I know the pain."GET REAL-TIME UPDATES AT THE FOX NEWS TRUE CRIME HUBThe two men forged a bond through the disappearances of their children, with Petito ultimately traveling to Arizona in April of this year to help search for clues surrounding Daniels disappearance."He called me in January and said, Dave, I want to be a part of the search," Robinson told Fox News Digital. "He said I dont want it to be about Gabby. I just want to come in as a friend to come out here to help you."Petito is celebrating the resurrection of evidence in Robinsons case, telling Fox News Digital the addition of new investigators is "fantastic.""I really pray for him and his family," Petito said.Robinson continues to advocate for missing Americans throughout the country, and he is pushing for new legislation to create federal standards regarding law enforcements response to missing-persons reports while running for a seat in South Carolinas Second Congressional District."The only thing that kept me straight is my love for my son and my military training," Robinson said. "I had to rely on military training to look at my son as a mission, and I put the mission first."