Shares of Robinhood Markets Inc. had mostly disappointed the trading app’s fans since their initial public offering. But Harsh Patel felt sure that was about to change.
Mr. Patel, a 27-year-old nurse in Columbus, Ohio, figured its price would rise after he saw chatter about Robinhood light up a stock market chatboard. So on Aug. 4, he paid $600 for a call option—a contract that confers the right, though not the obligation, to purchase 100 shares at a stated price by a certain date.