These officials, whose work was kept under wraps at the time, were assigned by Timothy Geithner, then president of the New York Fed, and Christopher Cox, then the S.E.C. chairman, to monitor Lehman in light of the near collapse of Bear Stearns.

Similar teams from the S.E.C. and the Fed moved into the offices of Goldman Sachs, Morgan Stanley, Merrill Lynch and others.

There were plenty of reasons to send in these SWAT teams. With investors on edge about the veracity of valuations on Wall Street — and with hedge fund managers like David Einhorn publicly questioning Lehman’s numbers — the government examiners rifled through Lehman’s accounts. They also interviewed executives about various decisions, and previewed the quarterly earnings reports.

Yet now, two years later, we learn through a 2,200-page report from Lehman’s bankruptcy examiner, Anton R. Valukas, that the firm was taking a creative approach with its valuations and accounting.

One crucial move was to shift assets off its books at the end of each quarter in exchange for cash through a clever accounting maneuver, called Repo 105, to make its leverage levels look lower than they were. Then they would bring the assets back onto its balance sheet days after issuing its earnings report.

And where was the government while all this “materially misleading” accounting was going on? In the vernacular of teenage instant messaging, let’s just say they had a vantage point as good as POS (parent over shoulder).

The new mystery is why it took this long for anyone to raise a red flag. “Even though Lehman dressed up its accounts for the great unwashed public, it did not try to fool the authorities,” Yves Smith, the author of “ECONned: How Unenlightened Self Interest Undermined Democracy and Corrupted Capitalism,” wrote on her blog last week. “Its game-playing was in full view.”

Indeed, it now appears that the federal government itself either didn’t appreciate the significance of what it saw (we’ve seen that movie before with regulators waving off tips about Bernard L. Madoff). Or perhaps they did appreciate the significance and blessed the now-suspect accounting anyway.

Oddly, when the bankruptcy examiner asked Matthew Eichner of the S.E.C., who was involved with supervising firms like Lehman, whether the agency focused on leverage levels, he answered that “knowledge of the volumes of Repo 105 transactions would not have signaled to them ‘that something was terribly wrong,’ ” according to the examiner’s report.

There’s a lot riding on the government’s oversight of these accounting shenanigans. If Lehman Brothers executives are sued civilly or prosecuted criminally, they may actually have a powerful defense: a raft of government officials from the S.E.C. and Fed vetted virtually everything they did.

(...) Lehman’s shell game didn’t come to light until June 2008, when a lower-level executive named Matthew Lee sent a letter to management raising a host of questions about the firm’s practices. (By the way, the S.E.C. and Fed were still working inside the building at this point.)