Board Thread:General Discussion/@comment-9219983-20131108055117/@comment-9090085-20131116022140

Looking closer at the scene, Penny didn't have her backpack when Ruby was shot by Roman, only to have it on her back a few seconds later.

If people are fine with a little crackpot:

I originally thought Penny's "backpack" unfolded from inside her back (her suspenders looked a little like a closed hatch to me), since many weapons in this series take up less space then you'd think (How many clips can Ruby's ammo pouch hold when it's smaller than a single clip? Several, I would assume.), that made some sense to me. Why it would pop out of her back, I can't imagine.