It turns out the missing Australian ingested MDMA (ecstasy) or NBOMe (hallucinogen) with his friend in Lapa and suffered a psychotic episode. They were so paranoid that they left the hostel for the airport without tickets (fearing the other guests were after them). At the airport they argued then the missing person took a cab to Copacabana and rented an apartment for 3 days. He left his belongings in the apartment and the next day was seen (injured and disoriented) by a fisherman on an uninhabited island 900 meters off of Leme. This was on the 22nd of May. A subsequent search of the island revealed nothing.

This had nothing to do with criminals or cabs. Self-destructive behavior resulting in a sad ending for all.

*Update* 8th of June, a body has been found on a beach on the Niteroi side of the bay with similar clothing to the missing person. A DNA test is pending.