News outlets aplenty buzzed last night after Berkshire Hathaway (NYSE: BRK-B) released its 13-F filing, detailing what stocks Warren Buffett's company bought and sold during the last quarter.

Among the big news: Berkshire completely sold out of Bank of America (NYSE: BAC), Becton Dickinson (NYSE: BDX), Comcast (Nasdaq: CMCSA), Fiserv (Nasdaq: FISV), Lowe's (NYSE: LOW), Nalco, Nestle, and Nike (NYSE: NKE). All of 'em. Gone. Liquidated.

However, Buffett himself almost certainly wasn't selling these companies -- or buying them to begin with. All of these positions were relatively small, and whenever Berkshire owns a small position, it's usually the work of Buffett underling Lou Simpson, who ran GEICO's investment portfolio. Simpson retired at the end of last year, which explains why so many of his likely positions were recently liquidated.

Simpson's investments flew so low under the radar that Buffett appeared to forget about them himself. In 2009, he told Fortune that "We own stock in four banks: USB, Wells, M&T, and SunTrust." Asked later why he omitted Berkshire's 5-million-share stake in Bank of America, Buffett told CNBC that he had nothing to do with it. Simpson did. So there.

In 2004's annual letter to shareholders, Buffett said this about Simpson's investment moves:

You may be surprised to learn that Lou does not necessarily inform me about what he is doing. When Charlie and I assign responsibility, we truly hand over the baton -- and we give it to Lou just as we do to our operating managers. Therefore, I typically learn of Lou's transactions about ten days after the end of each month. Sometimes, it should be added, I silently disagree with his decisions. But he's usually right.

With Simpson now retired, there's now another Buffett underling to watch: Possible successor Todd Combs, who will start managing $2 billion to $3 billion of Berkshire's money in the near future. Get ready for more 13-F confusion.

Fool contributor Morgan Housel owns shares of Berkshire and Bank of American preferred. Becton, Berkshire Hathaway, and Lowe's Companies are Motley Fool Inside Value picks. Berkshire Hathaway and Nike are Motley Fool Stock Advisor recommendations. Motley Fool Options has recommended writing covered calls on Lowe's Companies. The Fool owns shares of Bank of America, Berkshire Hathaway, Fiserv, and Wells Fargo &. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.