The hellish week of one short seller. : Last Monday, Nate Koppikar, portfolio manager of hedge fund Orso Partners, woke up at 4 in the morning to check his home Bloomberg terminal. His computer had flagged that GameStop shares would open much higher than normal on the stock market, but he didn’t make much of it. Although Koppikar wasn’t betting for or against GameStop, he knew how much other Wall Street hedge funds were cheering for the company’s demise.