"We do not know where he is at this moment," said James Brosnahan, Mr. Hsu’s lawyer. "We hope he will be court today."

Mr. Hsu’s absence seemed to be a repeat of his disappearing act in 1992, when he skipped out on a sentencing hearing related to his conviction in a fraud case, only to re-emerge years later as a major Democratic fund-raiser in New York. Since 2003, he personally contributed $600,000 to Democrats around the country and raised hundreds of thousands more, frequently hosting fund-raising parties and getting his picture taken with prominent politicians.

He was a designated "Hillraiser" for Mrs. Clinton’s presidential campaign, meaning he had bundled over $100,000 in contributions from others. Last week, the Clinton campaign said it was given to charity $23,000 Mr. Hsu had donated, and was reviewing other contributions he helped raised for any evidence of illegality.

Also last week, Mr. Hsu resigned from the board of the New School in New York, where he had served as a trustee and a member of the board of governors of the Eugene Lang College there.

Mr. Brosnahan told reporters outside the courthouse in Redwood City that he had sent an assistant to Mr. Hsu’s apartment in New York on Tuesday to retrieve Mr. Hsu’s passport, but it could not be found.

Ralph Sivilla, an assistant California attorney general, said the government had believed that the $2 million bail and Mr. Hsu’s agreement to remain in the country were sufficient to ensure that he would not flee.

"Those circumstances seemed to suggest he was not a flight risk," Mr. Sivilla said. "I don’t know at this point what our next step will be."

Asked whether Mr. Hsu could have left the country, Mr. Sivilla said "I would imagine he has the capability," although he added that he had no reason to believe that Mr. Hsu had done so.

Mr. Hsu’s latest disappearance deepens the mystery surrounding much of his life since he vanished 15 years ago. He apparently spent part of the 1990s in his native Hong Kong, where he managed a garment company, before returning to the United States and taking up residences in California and New York.

On campaign finance reports, he has listed his occupation as an executive at an assortment of companies that appear to be connected to the apparel trade, although efforts to verify his involvement with them have proven fruitless. An address he has given as his office in New York’s garment district seems to be little more than a mail drop, and people who work nearby have said they rarely see him.