Apple CEO Steve Jobs was spotted by a Reuters reporter at the company's headquarters in Cupertino, CA Monday, lending credence to speculation that he has already returned to work. The report comes days after a Wall Street Journal article claimed that Jobs, who is also the largest stockholder in the Walt Disney Company, had undergone a liver transplant in Virginia two months ago. "This is the first time we've heard from Steve Jobs since he reported he was taking medical leave," Oppenheimer analyst Yair Reiner told Reuters. "It's a sign Apple has its CEO back." But Susquehanna Financial Group analyst Jeffrey Fidacaro told the wire service that some investors still have concerns about Jobs's health. "He's obviously the clear visionary of the company," Fidacaro said. "There is a concern about his health and what Apple has told us about his health and what role he'll be playing when he returns."