(NewsNation) — It’s been nearly 16 months since Daniel Robinson, then a 24-year-old geologist in Arizona, went missing.

His father, David Robinson, hasn’t given up on trying to find him, even though police say there’s no evidence of foul play and have resisted a deeper investigation.

“I gotta do my job and find my son,” David Robinson said. “He’s my son. I’m his father. It’s my job.”

Even the private investigator is no longer on the case — but David Robinson has convinced an outside agency to go through Daniel Robinson’s computer and cell phones for any clues.

His jeep was found a month later, crashed in a desert ravine. Robinson’s keys, cellphone and wallet were still inside and his clothing was in a pile just outside the vehicle.

The investigator who David Robinson is working with, Jeff McGrath, took NewsNation’s Nancy Loo to the crash site.

He said the vehicle was tipped over on the passenger side, but there was no red paint in the area around it.

“That’s why I’m saying that vehicle did not crash here,” he said. “Its last place of rest was here, but something was going on with that vehicle.”

In addition, McGrath said, there were 11 additional miles and 46 additional ignition cycles on the jeep from after its airbags deployed.

While David Robinson waits for information on his son, he has held vigils and organized dozens of searches, covering more than 23,000 acres on four-wheelers and on foot.

On at least two separate occasions, volunteers found human remains which turned out not to be Daniel Robinson’s.

Although they didn’t find his son, David Robinson said it does bring him a little relief that they were “able to bring some other families some type of closure.”

Now, David Robinson has been raising money on GoFundMe (almost $306,300 as of Wednesday) and takes every opportunity to speak about his son’s disappearance, including at CrimeCon in Las Vegas.

He’s also created a robust social media presence, a podcast, and a website documenting the case.

David Robinson said he feels blessed to have a platform.

“In doing so, I’m able to also help other families,” he said.

This army veteran now has a new mission in life — one he says he’ll never give up.

“Soldiers say they don’t leave anyone behind,” David Robinson said. “He’s my son, and I’m definitely not leaving him behind.”