If you go here:
http://www1.hilton.com/en_US/hi/cust...o#PersonalInfo
you will find this...
Personal Information We Collect
At every touch point or guest interaction, we may collect personal information. In addition to any other information you may choose to provide to us, this personal information may include: your name and contact information; date of birth; preferred communication methods; business name, title and business address; credit card details, including the three-digit code that appears on the back of your credit card; member number, frequent flyer or travel partner program affiliation; date of arrival and departure; room and vacation preferences; travel history; and details on hotel, airline and rental car packages you book. We may also record details on joint travellers, including their names and frequent flyer numbers, and the age of the driver of the rental car.
I would still be suspicious. The only data that Hilton asks me for to verify my identity is my telephone number and, sometimes, address.
I would call 1-800-HILTONS (1-800-445-8667), ask for Guest Assistance, explain your concern and ask them who you should speak with to determine the legitimacy of this request.