Yes, booking.com did get hacked.
Was talked about on here for a while, people who had confirmed bookings, and had paid, were sent messages, some from odd places, as yours, asking for more $.
Sad really, I was with booking.com for a while, got to silver status.
Will not be using them anymore.
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Its gotten so bad, that the scammers know, when and where a person has booked, and you cant tell me its just by chance the scammers know it.
In your case, if they have gotten the date of your stay right, and then name of the hotel/resort right on spec, then its a very deep result that the scammers have gotten.
Bad, mate, very bad.
As you have replied to them, probably your details will now be onsold.