BUCKEYE, Ariz. (NewsNation Now) — The family of Daniel Robinson, 23, is hoping against the odds that their son, missing for six months, is still alive. But frustration is growing at the effort by local police to find answers.

Jeff McGrath is a private investigator who is working with Robinson’s family to figure out what happened to him. In late July, Robinson’s Jeep was found crashed in a ravine.

“We’re saturating the homeless populations, the homeless communities in the valley,” said McGrath. “The reason being is if there was some type of a disorientation or head injury that could still be going on, and Daniel just doesn’t really know who he is.”

Robinson’s father, David Robinson, said the only solid new lead is that someone claims to have seen Daniel on June 23.

“We do have now a second person who saw my son on June 23. This person is a federal law enforcement agent who can give us a better understanding of the timeline,” said David Robinson.

He said that law enforcement official was out target practicing with his children when he saw Daniel. 

“[The law enforcement official] approached, my son was mild-mannered, they had a long conversation with him,” David Robinson said. “It appeared that he was cleaning his car — the car that had been damaged. My son directed him to a location that’s better suited for target practicing.”

McGrath said much of the case doesn’t add up. Data shows 11 miles on the vehicle after the airbags deployed and more than 40 attempts to start the engine after it crashed. He’s certain there was actually another crash somewhere else.

“It tells me there’s a second crash location, or I should say a first crash location at minimum. And then there’s the recovery location where the vehicle ended up driving down into the ravine and coming to rest at the bottom on its side,” said McGrath.

Robinson’s keys and wallet were still inside the Jeep and his clothing was found in a pile just outside the vehicle. McGrath believes that points to Robinson being disoriented, but he hasn’t ruled out foul play or the possibility of drugs being involved.

“And [drugs] would cause inhibitions to go away, possible risky behavior. He may have hit his head in an accident had some traumas and brain trauma … some swelling of the brain,” said McGrath.

Volunteers have repeatedly fanned out over the desert searching.

McGrath admits the chances that Robinson is alive are slim. But he shared the Robinson family’s frustrations about how the case was handled from the start. 

“[The police’s] theory is that nothing happened. Nothing. There’s nothing wrong here. And there’s nothing suspicious here,” said McGrath.

The Buckeye Police Department provided the following statement to NewsNation.

“Daniel’s disappearance is heartbreaking. Detectives with the Buckeye Police Department investigate every lead in this case. This investigation will remain open and active until we find Daniel,” Buckeye Police Chief Larry Hall.

Anyone with information on Daniel Robinson’s whereabouts is asked to call the Buckeye Police Department at (623) 349-6400.