The husband of a 69-year-old woman who vanished during a desert hike is pleading for her safe return.

Barbara Thomas, a grandmother from Bullhead City, Arizona, was wearing a bikini top and had no supplies or cellphone when her husband says they became separated in 90-degree heat in the Mojave Desert on July 12.

In an interview with Inside Edition, Robert Thomas said he believes someone took Barbara when he lost sight of her during their hike.

"If anyone has her, I would just beg that they would release her, no questions asked," he said, becoming emotional. "I just want her back ...."

Robert says they had taken a short trip in their camper when they decided to pull up and go for a 2-mile walk to explore rock formations. They took a pack, beer and a gallon of water, and Barbara was wearing a bikini, hiking boots with black socks, and a red-and-white baseball cap.

They were on their way back to the camper when Bob said his wife started pulling ahead. He told her he wanted to take a picture of a rock formation and as he put his camera away, he saw her rounding a corner.

"That’s the last I ever saw of her," he said.

When he reached the corner and didn’t see her, he assumed he’d find her sitting outside their camper, he said. But when he got to the vehicle, the door was locked.

"I hollered her name and I waved my arms, and I looked around the area and I saw that she wasn’t anywhere around. She didn't respond. I got really panicky," he said.

He called 911 and authorities came to the scene. Search crews, including sheriff's deputies, K-9 officers and a helicopter, have been looking for Barbara in the days since. On Wednesday, about 20 people continued the search.

"I feel like someone did pick her up because she was wearing a bikini, she had a beer in her hand and she was ahead of me and she had to cross that road," he said.

Thomas said the police consider him the prime suspect "because it was just the two of us." He went for a polygraph test and authorities told him he was being deceptive, but Thomas said he had not had any sleep when he took the test.

Speaking to Inside Edition, he insisted he had nothing to do with her disappearance.

"She is the love of my life," he said. "Come home. We're missing you."

Barbara Thomas is 5 feet, 9 inches and 130 pounds, with blonde hair and green eyes. Anyone with information regarding her whereabouts is asked to contact the Colorado River Station at (760) 326-9200 or sheriff's dispatch at (760) 956-5001.

RELATED STORIES

How to Survive Getting Lost in the Woods

Woman Survives 6 Days in Arizona Desert After Car Crash Leaves Vehicle Trapped in Tree

Man Survives in Desert For Days on Beer, Crackers and His Own Urine