Bao Fan, a renowned investment banker in China, has disappeared and is unreachable, raising concerns that Beijing’s crackdown on the country’s business elite is continuing. In a filing to the Hong Kong Stock Exchange on Thursday, China Renaissance Holdings said that it has been unable to contact Mr. Bao, the company’s chairman and chief executive. China Renaissance said its board was “unaware” of any information that indicated his disappearance was tied to the company’s operations. The company’s share price plunged on the news, falling 28 percent on Friday. The disappearance of Mr. Bao, a well-connected deal-maker known for his close…