BUCKEYE, Ariz. (NewsNation Now) — David Robinson is on the biggest mission of his life.

After serving two tours in the deserts of Afghanistan, the Army vet is now in the deserts of Arizona, and has no plan to leave until he finds his 24-year-old son, Daniel Robinson.

“I’m a professional soldier,” he said, three months since his son went missing in Buckeye, a western suburb of Phoenix. “I have to do my job. Find my son. He’s my son. I’m his father and that’s my job.”

The search has been filled with frustration.

The terrain around Buckeye where Daniel Robinson’s vehicle was found is remote and treacherous.

And whether Daniel Robinson was even in the vehicle when it crashed is now being questioned.

“I have faith and I really believe I’ll have my son back alive,” his father said.

Daniel Robinson is a geologist who was last seen leaving a remote worksite in Buckeye, where he was analyzing rock samples on the morning of June 23.

“He was living his dream,” his father said. “He came here interested in geology his first year in college, freshman year. He took a class and that just set it off.”

His father describes Daniel Robinson as always friendly and well-adjusted despite having been born without a right hand.

“He don’t wear prosthetic,” his dad said. “His mom tried to get him to wear it. ‘No mom, I don’t want to … be who I am.’ That’s just Daniel.”

A month after Daniel Robinson’s disappearance, a rancher found his Jeep wrecked in a ravine. His keys, wallet and phone were in his Jeep, but there was no sign of him.

“I think the first thing he would’ve done, if he were in that vehicle, at least carry his phone with him,” David Robinson said. “That’s one thing I couldn’t imagine; someone 24 years old won’t be attached to his phone?“

The Robinson family hired Jeff McGrath, of 3Laws Recon Investigations, to look into the case. McGrath is miffed that Buckeye police have already ruled out foul play.

“I don’t think Danny was in that vehicle,” the investigator said.

McGrath pointed out that “the vehicle had 11 additional miles on it from when the airbags deployed. It had 46 additional ignition cycles on it after the airbags deployed.”

McGrath also noted red paint had transferred onto the right side of the jeep.

“There’s no red paint in this area,” he said as he gestured to the vast desert. “That’s why I’m saying the vehicle did not crash here. The vehicle, its last place of rest was here, but something was going on with that vehicle.”

The Buckeye police department refused an interview request but provided its report, in which co-workers said Daniel Robinson made odd comments about needing rest before he left the job site that morning.

David Robinson, who is retired and is funding his search, in part, though a GoFundMe account, said his son was even-tempered and always saw the bright side of things.

McGrath told “NewsNation Prime” on Wednesday that police turned all the evidence they collected over to him since they did not have enough to prove a crime happened.

“I’ve never seen [police do that] in my career in law enforcement or as a private investigator,” McGrath said.

Just like the Gabby Petito case, internet sleuths are piecing clues together.

Bryan Watts hosts a mystery and adventure show on YouTube that recently featured Daniel Robinson’s disappearance

“Just seeing the way the car was, the Jeep was, and the evidence, to me, it actually does support foul play,” Watts said. “I then got lots of comments from people in and around that area that said, yeah there’s crime, carjackings that happen all the time. It’s bad; something they’re aware of.”

Searching on his own practically every day for over three months and organizing volunteer searches, David Robinson is a man on a mission to find his son and will remain in Arizona until there are answers.

“I don’t know what to think anymore. Just going to keep on watching and keep on searching,” he said. “Treat this like a mission. Keep saying it.”

A major ground search is planned for this weekend with a crew of more than 1,000 volunteers. Anyone with information about the case is urged to click on pleasehelpfinddaniel.com or call (803) 200-7994.