What I understand about shorting is that you to eventually have to Cover, which is a when you pay for the stock at a lower price for the profit.
The brokerage that lent those share uses the money from the Cover to buy back the stock and give it back to the original owner they borrowed the shares.

I would think you would have a Spring(or rubber band effect). The Spring is were they all cover in great quantity. The part I don't get is when they cover. I figured they only hold a short position for a few days.