Pheobe Bishop was last seen near Bundaberg airport in southern Queensland about 8.30am on May 15 after booking a trip to Western Australia.
Police have been combing through Gin Gin, an area near Bundaberg, for information about the teenager's whereabouts after recently abandoning a search in a national park.
As the search for the missing teen reaches two weeks, a man identified as Pheobe's housemate, James Wood, has been charged with unrelated weapons offences.
Police allegedly found a shortened firearm and ammunition during a search of a grey Hyundai ix35 and a Gin Gin home.
The home - where Pheobe lived with two others - and the car, which was thought to have been used to take the teen to the airport, were declared crime scenes in the disappearance investigation.
Wood, 34, was charged on Sunday with one count each of unlawful possession of weapons (short firearm) and authority to possess explosives.
He was issued with a notice to appear before Bundaberg Magistrates Court on June 13.
Another woman believed to be living with the teen, Tanika Kristan Bromley, was also charged with weapons offences concerning a shortened firearm, ammunition, and two replica handguns found in a search of the car and home.
She was granted bail at Bundaberg Magistrates Court on Tuesday.
Police have said the weapons charges were unrelated to Pheobe's disappearance and there was no suggestion Bromley or Wood were involved.
Police are still endeavouring to find out what has happened to Pheobe, with the investigation focusing on Gin Gin, where the teenager lived.
A search in Good Night Scrub National Park, an hour's drive from the airport, had been the focus for investigators over the past week with homicide detectives, police divers and cadaver dogs scouring the bushland.
Some items believed to be linked to the investigation were seized for forensic examination.
The search also revealed evidence that might have been moved from the national park before police arrived.
Police are still appealing for anyone with information - particularly regarding the movements of the grey Hyundai between May 15 and May 18 in the Gin Gin area. - to come forward.
Pheobe's mother has been consistently pleading online for information to help find her daughter as the investigation drags on.
Kylie Johnston last shared an insight into her daily struggle as she held on to hopes that Pheobe would return home.
"Finding it hard to get out of bed today, to find the strength to put one foot in front of the other and know what to do, what to think or what to say," she posted on Facebook on Tuesday.
Pheobe is about 180cm tall with a pale complexion, long dyed red hair and hazel eyes.
She was last seen wearing a green tank top and grey sweatpants, and carrying luggage.
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