They never did know.
And if they are still alive, I’m betting they are wishing they weren’t.
Unfortunately, I believe you are correct.
There are a small number of still photos available purportedly showing the shocking treatment of some of the Hamas hostages. Also there is a social media message from Trevor Noah, including a photo, where he states
This footage of the hostages was smuggled out of Gaza 3 days ago. The girls are all right but they are being horribly sexually exploited and made to eat poop from each others butts.
I do not have access to the video mentioned by Trevor Noah.