Jane Brister, a Koala Rescue Specialist at Fauna Rescue SA, was called to a suburb in Adelaide last week after a driver reported hearing "unusual sounds" and "crying" coming from his car.

The driver had driven from his home in the Adelaide Hills district to the city, a trip he estimated to be nearly 16 kilometres, according to Brister.

"Early in his journey, an oncoming driver flashed his lights at him, and so he thought there must be something wrong with his car," Brister said. "But [when] he pulled over... he couldn't find anything in the dark."

When he arrived in Adelaide, he heard "crying" coming from the car and soon spotted the small koala stuck under the hood of the wheel.

A local Metropolitan Fire Services crew attended the scene to help remove the wheel, and allow Brister to coax the koala out.

"[At first] I could really only see her face and one paw," Brister said. "She was pinned behind the wheel, but fortunately not amongst the axle.

"It took a lot time and patience to get her out."

Since nearly 80 per cent of koala road trauma incidents are fatal, Brister said she had "expected the worst".

She was relieved to find the traumatised koala had survived the incident with only some minor abrasions and "singed fur".

"I just couldn't imagine that if she had been in there for 16 kilometres she wouldn't have serious injuries," she said.

But sadly, examinations of the koala by a veterinarian revealed the koala had lost a joey.

"We continued a search for a couple of days, but haven't found any evidence of the joey at all," Brister said.

"It's a very sad part of the story, as it was in addition to the trauma she must have gone through under the car."

Brister said it remains "a mystery" how the koala became stuck.

"We don't know how she got in there," Brister said.

"Koalas don't normally crawl up into that spot [under the wheel], and the driver... did not feel he had hit anything."

The koala, named Kelly - after one of the firefighters on duty on the night - was released on Friday into an area with "lots of eucalyptus trees", after spending a week recuperating with the Fauna Rescue team.

"At the end of the day it's just incredibly lucky she survived, and it was great to be able to send her home," Brister said.

"She's a very very lucky girl."