A mum who was rescued in a national park after going missing for 12 days with no food had hit her head on a tree and become disorientated, her daughter said.

Experienced hiker Holly Suzanne Courtier, who was working as a nanny, disappeared on October 6 during a trip to Zion National Park in Utah.

A massive search was launched using sniffer dogs, drones and specialist teams that scoured the rugged nature preserve on foot.

Park rangers found the 38-year-old, from Woodland Hills, California, after she was spotted by a hiker on Sunday, but did not say where she had been or how she survived during the 12 days.

Holly was missing for 12 days in a national park in Utah

Her daughter Kailey Chambers has since revealed she hit her head on a tree and was too weak and disorientated to seek help.

"She injured her head on a tree," Kailey told CNN.

"She was very disoriented as a result and thankfully ended up near a water source -- a river bed. She thought her best chance of survival was to stay next to a water source."

"She was too weak and disoriented (to seek help). She was unable to take more than a step or two without collapsing."

Daughter Kailey

Kailey said her mum was so dehydrated she could barely open her mouth.

"She is still weak but recovering," she added.

"We are slowly introducing foods. Her health remains our top priority.

"My mom's recovery is my top priority right now. ... We will continue to focus on her health and will update everyone when possible.

"She lost her job as a nanny due to coronavirus. The family could not afford to keep paying her. She made that a positive thing, said that gave her the time to get out, see the parks."

The mum was missing in Zion National Park in Utah

After not hearing from her for a week, Kailey travelled 500 miles to try and find her mother.

After she vanished, Holly's family setup a GoFundMe page to raise funds for the search and any medical expenses.

It has so far raised more than $12,000.

And update post on the page read: "Thank you to everyone for their continued support towards Holly's recovery.

"I am Holly's older sister, Jaime Strong, and reside in Simi Valley, California. I set up the Go Fund Page to help aid in the expenses our family and volunteers were incurring in the search and rescue of Holly. In order to provide as much transparency as possible, I am detailing what your donations will be used towards.

Holly was "alive and well" but needed medical help, her sister says

"Funds will be used to reimburse the family and friend's costs in searching for Holly. (Such as; hotels rooms, equipment purchased to look for Holly, car rentals, and food for search parties.

"A separate bank account will be opened up to reimburse these individuals.

"A remainder of the donations will be used to cover the medical care applied to Holly during her hospital stay as well as therapy costs moving forward."

Daughter Kailey says her mum is an experienced hiker

Speaking to Good Morning America on Monday, Jillian Courtier-Oliver, of of Holly's sisters, admitted she lost hope that they would find her.

She said: "It wasn't until two days ago I actually said, 'I'm starting to lose hope.'

"They had a lot of cadaver dogs out and I knew what they were looking for was a body, not a person. It was the first time I actually started losing hope. And I went with up with so much help knowing that we needed to find her.

"I knew if anyone could do it, it was going to be her. She's such a fighter."