What could have gotten the chickens?

Hi folks,

This is my first post to this forum. Its not strictly a farm question but
I figured someone out there might know. I raised some chicks for
a friend who wanted to get started raising hens for their eggs.
She started with a pre-built garden shed & had her husband cut an
opening to let the chickens get into a fenced in area. He buried the
chicken wire and covered the 6' high fence with netting (so the top was
completely covered by the bird netting). Apparently there are
some areas where the netting is not afixed to the fence (just flapping
over).

They had 7 chickens (about 12wks old & Rhode Island reds & other full
size, not bantums). They went away for the weekend and came back to
find no chickens. There are a few feathers in the yard but no "carnage"
like I've had when a fox or raccoon got mine. No carcass, no blood, no
feet or wings. Just a few feathers.

What could have gotten them? Could these 12wk hens have figured out
where the areas of the netting weren't afixed to the fence and flown out?
(I don't think these guys were much of flyers. They never flew much at my
place - just a few feet at most).

What would have completely eaten every part of the seven chickens?
If you can't help us, we're going with Alien Abduction!

Thanks
Tam