Michael Atakelt was 22 years old when he disappeared on June 26, 2011.
Two weeks later his body was hauled from the Maribrynong River at Ascot Vale, in Melbourne's west.
Victorian Coroner Ian Gray delivered an open finding and ruled the cause of death was "consistent with drowning".
The coroner ruled out suicide but said drug use and foul play were possibilities.
Atakelt's father, Getachew Seyoum, has long maintained his son was murdered, possibly by being drugged.
Outside court today he expressed disappointment at the coroner's finding.
"I can't be happy with the decision, [but] I can't be unhappy with the decision actually," he said.
Michael Atakelt was in police custody in the days before he died and the coroner noted a perception in the Ethiopian community that local officers were involved in the death.
He found there was no evidence to prove this, although he said local police should not have been assigned to investigate the case.
Judge Gray made a number of recommendations to Victoria Police, including training on cultural factors which might affect the way families are told about a death.
The case officially remains open.