SHANGHAI  A Chinese businessman named Zhao Danyang paid a record $2.1 million in a charity auction on eBay last year to win a lunch date with one of his heroes: Warren E. Buffett, the so-called Oracle of Omaha.

This was a chance to get close to the world’s greatest stock picker, Mr. Zhao says, and to pick his brain about investing, the global financial crisis and philanthropy.

But a day before the lunch, which took place on June 24 at the Smith & Wollensky steakhouse in New York City, Mr. Zhao told the media he would offer Mr. Buffett a stock tip of his own: a little-known Chinese retailer called WuMart.

“I didn’t want to influence the market,” Mr. Zhao, 37, said in a telephone interview Friday. “It was just a tip from a friend.”