The note says call for help and you just woke up in a tub full of ice. Okay, this is a little far fetched. Lonely guy meets beautiful woman,
takes her back to his hotel room, wakes up in a tub of ice with a note that says he should call paramedics immediately. He realizes he has been cut open and his kidney removed for sale on the black market.
This myth mostly comes from stories from India and other third world countries where black marketeers harvest kidneys from isolated individuals. This could be associated with the transient population that moves through Las Vegas. Many people blow into town alone, with no one knowing where they are. This person would be an ideal target for a black marketeer to make just disappear. So why bother leaving them in the tub? Besides, 2 kidneys are better than one.