Day’s husband, Ernie Caswell, was hospitalized at the time and reported him missing after Day stopped visiting, Dateline reported.
A roommate who had been living with the couple reportedly told authorities that before Day disappeared he left their home on foot to visit friends, Dateline reported.
But Day’s car was later found with two people on the Oregon coast, NBC affiliate KOBI reported. It wasn't clear how the people, who were not identified, gained access to it, according to the station.
Phoenix is in central Oregon, south of Medford.
Police searched Day’s home, a nearby graveyard and a creek for traces of Day but found nothing, Adkins told Dateline.
“They said they brought in cadaver dogs, too,” she added. “But they never found anything that would imply a crime had happened.”
Adkins said that Day’s family — most of whom live in California — didn’t find out that he was missing until several months after he vanished, when a relative saw a local television news report about it.
At the time, Caswell was hospitalized with dementia and hadn't been able to provide contact information for his family, Dateline reported.
Local authorities, meanwhile, reportedly told Adkins that they had no record of other relatives, according to the show.
"We are devastated,” Adkins told Dateline. “We had no idea anything was happening and six months into it, we figured it out. We should have been notified.”
Local authorities have not responded to previous requests for comment.
Tim Stelloh is a reporter for NBC News, based in California.