apparently a member of the public saw one ? two of the bodies on the saturday, so about 12 hrs after they were last heard from, but did not approach and assumed it was people dozing.
this is not uncommon in open land.
this was after their relatives had reported them missing.
the crime was not discovered until 24 hrs later, about 1pm on the sunday.
just think of the evidence that might have been lost in the interim. police eventually found one of their mobile phones in a pond some time later.
it was not a large gathering, or disorderly/drunken. it was a birthday party for the older sister, Bibaa who was a senior social worker. they were both responsible people with regular lives and habits.
the passing woman who first glimpsed the bodies had no reason to report it at the time.
if at least a police person had been walking about, asking people if they'd been there the night before, had seen or heard anything, anyone suspicious about...
and it does not seem to have had the coverage normal in such cases. in fact this case is most unusual.
police know it was an unknown killer, who would have injuries. maybe someone saw something that could have been relevant, but as time passes, and without much publicity, the best chance is gone. RIP Bibaa and Nicole.