Nope it is a regular confirmation and there is no language that states it has to be paid. Hilton Honors Diamond desk says it is out of their hands due to this clause in their terms and conditions.

We reserve the right to cancel or modify reservations where it appears that a customer has engaged in fraudulent or inappropriate activity or under other circumstances where it appears that the reservations contain or resulted from a mistake or error.

They screwed up...they didn't require payment in advance. However this clause reads to me as if it is something done on my end not theirs.