Do you have a link to this. I haven't seen it documented yet.
If so, she was probably drugged.
Need to find the body
It looks like the original report of that info comes from an Aruban site, according to this link:
http://www.legendgames.net/showstory.asp?page=blognews/stories/WN0000183.txt
"An online newspaper, AM Digital, hosted at Aruba.com has reported that the three men involved in the Natalee Holloway disappearance claimed to have had sexual relations with the 18 year old Alabama high school senior at the beach prior to returning her to her hotel at approximate 2 AM."