It sounds like “Wall Street” meets “The X-Files.” The stock market mysteriously plunges 600 points — and then, more mysteriously, recovers within minutes. Over the next few weeks, analysts at Nanex, an obscure data company in the suburbs of Chicago, examine trading charts from the day and are stunned to find some oddly compelling shapes and patterns in the data. To the Nanex analysts, these are crop circles of the financial kind, containing clues to the mystery of what happened in the markets on May 6 and what might have caused the still-unexplained flash crash. … The truth of what happened on May 6 could be hiding somewhere in those mysterious configurations. Or it may lie somewhere else entirely. But 15 weeks later, the authorities are still looking for it. The Securities and Exchange Commission and the Commodity Futures Trading Commission plan to issue a final report on their findings in September. A preliminary report in May blamed a confluence of factors, including worries over rising sovereign debt and a lack of marketwide circuit breakers, but the new report is expected to go further. For now, this much is known: The markets were already down and on edge that morning as Europe’s debt crisis seemed to be spiraling out of control.