Police and volunteers scoured the rugged coastline, interviewed campers and combed thousands of images and surveillance videos. A reward of 1 million Australian dollars (about $745,000) was offered for information that could lead to her safe return.
But authorities feared the worst: Australiaâs vast outback is full of remote trails from which it is easy to evade the outside world.
Early on Wednesday, they found her â alone in a locked room in a house in Carnarvon, just seven minutes from where she lived with her mother, stepfather and baby sister. A 36-year-old man was apprehended at a nearby property and taken into custody.
âWe were literally looking for a needle in a haystack, and we found it,â Acting Police Commissioner Col Blanch told a local radio station. âWhen she said, âMy name is Cleo,â I donât think there was a dry eye in the house,â he added.
Ellie Smith, Cleoâs mother, posted the news on Instagram, saying: âOur family is whole again.â
The little girlâs disappearance had gripped the nation. Family camping trips are routine in Australia, and abductions are extremely rare.
During the 18-day search, comparisons were drawn to other missing child cases â including 9-week-old Azaria Chamberlain, who vanished while her family was camping in the Australian outback in 1980. Her mother was found guilty of her murder and sentenced to life in prison, only to be released when new evidence surfaced that absolved her. A coroner later ruled Azaria had been snatched and killed by a dingo. Her disappearance was made into a 1988 film âA Cry in the Dark,â starring Meryl Streep.
âIt often is a tragic outcome, but this is great news and uplifting for the entire country, especially for those who put their life and soul into finding Cleo,â Western Australia Premier Mark McGowan said. âI was talking to the [police] earlier, and I said thereâd be movies made about this.â
Forensic experts also expressed surprise that Cleo was found alive â a rare outcome in such cases.
The case drew massive media interest and galvanized sleuths across the Internet, in a localized version of what occurred following the recent disappearance of Gabby Petito in the United States. Wild theories circulated on social media, and Cleoâs mother and stepfather were openly attacked.
Police said on Wednesday that there was no family connection to the man they arrested. They believe she was snatched from the campsite in an âopportunisticâ crime. Crucial to her rescue was evidence police received about an unknown vehicle at the campsite at the time of her disappearance, authorities said.
âInternet detectives jump to conclusions but our detectives, the real detectives, canât afford to do that,â Blanch, the acting police commissioner, said.
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