Thank you for the responses, and what [MENTION=1562]hfly[/MENTION] said, I believe is exactly the case here, which circles back to my original question.
Is there a $60 visitor charge company wide? The below exerpt from the Doubletree Cariari front desk manager's email to me seems to imply that, and Hilton hasn't denied it.
Actually Hilton has gone silent on this whole thing, and won't respond to my emails.

"I am very sorry for the inconveniences that you experienced regarding the charge for the visit of your friend. According to Hilton's policy all guests must be registered at the Reception for security purposes. When the name of the additional guest is not provided before or at the moment of the check-in an additional $60 fee applies."