FIFTEEN years ago, on a sweltering hot February afternoon, a call came through to The Northern Star newsroom ‒ a backpacker was missing in Lismore's CBD.

Nothing hinted at the heartbreak to follow, that a decade-and-a-half later we would still be asking "what happened to Simone Strobel?".

At the time, police reported the 24-year-old German backpacker, not long into a 12-month working holiday in Australia, had set up camp for the night at Lismore Tourist Caravan Park, on Dawson St, with boyfriend Tobias Suckfuell, his sister Katrin, and friend Jens Martin.

On Friday, February 11, 2005, the group spent the night at the Gollan Hotel, where they were captured on CCTV.

Her friends reported her missing the next day, saying she had gone for a walk after an argument with her boyfriend, and had not returned.

Dozens of SES workers joined police in combing streets and drains in Lismore's downtown area, but it would take another six days before Simone's body was found hidden beneath palm fronds at the bocce courts, just 90 metres from her camp site.

In the days and years that followed her 2005 death, the life and last known movements of the young tourist were laid bare ‒ but one question remained unanswered, who killed Simone?

Five years later, with Simone's killer still not found, an inquest was held in Lismore.

NSW Police told the inquest they believed Tobias had killed her by smothering her, most likely with a pillow, after they had argued.

They said they believed Tobias, most likely with Katrin's help, then carried Simone's body across the road where they stripped her before pushing her through a hole in the fence around the bocce club and hiding her under palm fronds.

Coroner Paul McMahon ruled there was not enough evidence to lay charges over Simone's death and issued a plea for Tobias and Katrin to give evidence.

"It seems fair and just that they be given the opportunity to tell their story, if for no other reason than to clear their names of the suggestion that they have had some involvement in the death of Simone Strobel," Mr McMahon said.

At the time of Simone's death, a grief stricken Tobias told The Northern Star, "I just can't bear it … anything could have happened" and he repeatedly denied having a part in Simone's death.

But both Tobias and his sister Katrin declined the plea to attend the inquest.

Their travelling companion, Jens Martin, returned to Lismore to give evidence.

Mr Martin told the inquest he had deferred to Tobias' insistence that he and Katrin lie about what happened without question, because he believed Simone was alive and would return.

He also said Tobias and Simone had fought bitterly on the night of her disappearance, a night when Mr Martin described Tobias as angrier and more aggressive than either he or Katrin had ever seen him.

Simone's heartbroken parents, Gustl and Gabi Strobel, said in 2012 it was "agonising uncertainty" not having resolution to their daughter's death.

Tobias returned to Australia when he married Samantha Moran, the daughter of a wealthy dentist, adopting her surname.

No one has been charged over Simone's death and the investigation into her death remains open.