I don't think Patsey wore the clothing all night. I THINK she changed but in the morning when she woke up in her pj's/or nothing, she had to put on some clothing quickly while the police were on their way their so she grabbed her clothing from the night before which was likely thrown on a chair in her room after she got home from Christmas night. No one would have had time to find a new outfit and put it on when they are in the same panic as the Ramsey's were. She just grabbed the clothes and put it on not thinking about a thing. It makes perfect sense.
It may be the disinfo that's going on, but I thought I read somewhere that she said that she was fully dressed when she discovered the note, so I thought she had already dressed before the panic. I think it came from her 'interview', or one of them, with the Boulder police that was finally held years later.
I never really discounted the possibility that Patsy or John did it, I just didn't see any evidence for it. That's why I thought about an accident and Burke. But now, barring evidence that one of them did it, I would say it's more likely an intruder. I don't know how to explain the clothing, though.