They went out to a party that night. They didn't have a party; they were leaving the next morning for a cruise and Disneyworld.
Someone could have entered the house.
I would be very careful of so-called "evidence" in the media since some of it was coming from Lee Hill, who is wanted for a felony.
I remember reading that they had a Christmas party at their house. Also I remember that Patsy said the son was asleep when they made the call about the missing girl but the son's voice could be heard in the background. True?