Immediately what comes to mind is that there was major disappointment from the brothel owner and his Yugoslav mates that the most stunning of the agency's girls, (of whom they were most proud, given her extreme good looks), had deliberately chosen not to show up for their booking, thus embarrassing the owner in front of international contacts and possibly raising their combined ire at her apparent impertinence, an act of defiance inspiring contempt, (as the lives of prostitutes aren't considered very highly in many places in Europe by members of crime gangs).
There's a possibility that after canceling the later appointment due to lack of time because of her 'cheating' the agency with her private booking with Samer, she was intercepted by a flunky working for the brothel owner and then taken, under duress, to these two Yugoslavs anyway.
There, as punishment for her 'disobedience' for canceling an important meeting with the two Yugoslavs and for the private booking with Samer being the cause, she was subject to the brothel owner's chastisement for deceptively cheating the agency out of its commission and, as punishment, after this she was handed over to these two Yugolsavs to suffer sexual degradation and retributive violence which may have possibly spiraled out of control and saw Revelle, inadvertently or deliberately, (as a warning to other prostitutes), murdered by these men, who then flew back to their home country completely unmolested due to NSW detectives' unwavering interest in her last client and his injuries as the main suspect.
Then again, without the presence of a body and apparently little effort made by the perpetrators to hide evidence of her abduction, Revelle may not have been, as suspected, murdered.
Since there have now been links made between this brothel owner and Yugoslav organised crime figures, there's also a chance that Revelle, who was known to be on the cusp of exiting the sex industry and signing with a major modeling agency, instead of being murdered, was actually human trafficked as a sex slave to somewhere in Europe or anywhere else outside of Australia.
Who knows if she isn't today still alive and being held captive under these circumstances?