It was just a quick comment by Warren before he decided against going any further.
My guess is Deutsche but who knows-besides Warren and Charlie, the bank etc., that is.
Here's the quick hit from the Omaha World-Herald:
What's the mysterious derivative position Buffett says would 'blow your mind?'
Warren Buffett says there is a time-bomb in the financial system, a badly mismarked derivative position, but he isn't saying where it is or who is on the hook.
The Berkshire Hathaway chairman and CEO made the startling proclamation while answering a question from a shareholder at the company's annual meeting Saturday at Omaha's CenturyLink Center — an all-day session attended by more than 30,000 people who come to hear the Oracle of Omaha testify about all things financial.
When asked about how he evaluates the derivatives exposure of banks Berkshire holds shares in, such as Wells Fargo, or those in which it has securities that one day will become share, such as Bank of America, Buffett unleashed a stunner.
He said he knows of one derivatives position unrelated to Berkshire — he didn't say who, when or where — that is very poorly accounted for. That usually means there is something wrong with the valuation of the derivative, perhaps a valuation that is outdated or which is based on flawed underlying assumptions or calculations.
"I know of one that would blow your mind," Buffett said.......MORE