Drunken Revels and Swan Maidens (again)

One of my friends had his birthday over the weekend.  When asked what he wanted, he replied "capture the flag!"  So they held a campout in which to play.  I couldn't go since I had to finish a paper for finals.  Anyway, it turns out that their party was a lot less "capture the flag!" and a lot more "get drunk and see how big we can make our fire".  It's pretty standard when you know my friends, so yeah...

The really interesting thing is that one of my friends this morning told me about two "really bitchy girls" who showed up about 2 AM in their campsite.  He also remembered that they were really, really attractive and somehow the line of group reasoning turned shortly to a "birthday present" for our birthday friend.  In the morning, they were gone and nobody remembered a thing about what happened, but his sleeping bag was covered with white down feathers.  Which gets me thinking...

Swan Maidens.  We've already been here once.  I get the feeling I know what went on.  Might as well call them werewhores.  The thing I want to know is, why do they keep finding my group of friends and what they want (apart from the obvious)?  Side note:  Why do people not notice or remember the preternatural things going on about them?  Is there something in normal people that just shades it from their minds?

Time to put on my detective pants.