Singenberger set up a Liechtenstein foundation for Canale, and helped him open an account at Wegelin, prosecutors said. By 2009, the account had grown to $1.5 million.

Canale, 62, is a Bronze Star recipient who worked for the Army as a field surgeon during Desert Storm in Saudi Arabia, Iraq and Kuwait, according to one of his lawyers, Martin Press. He also was a surgeon in Macedonia and Kosovo, Press said.

It is not clear from court records how Singenberger’s wayward mail enclosure -- which included such client details as their residences, their Swiss banks, and the ways they hid accounts from the IRS -- found its way to prosecutors.

Canale, who pleaded guilty Dec. 21 in New York, was surprised to learn of the existence of the Singenberger list, said his other attorney, Robert Fink.

A Surprise

Wajsfelner only learned at his March 5 sentencing that he came to the government’s attention through the misdirected list, according to his lawyer, Jeffrey Denner.

“That was definitely news to me and my client,” he said. “Beda Singenberger, to my understanding, is a figure who’s certainly put a lot of people in the frying pan. I don’t think a lot of people recognized they were so close to the fire.”

Ellen Davis, a spokeswoman for Preet Bharara, the U.S. attorney in New York, declined to comment.

Nothing prevents the government from using evidence that it obtains accidentally, said Jeffrey Neiman, a former federal prosecutor who worked on the UBS case.

“It proves that no matter how hard clients try to conceal assets overseas, darn human error can always get in the way,” he said.