It was a second-quarter earnings call for SunEdison, a solar-energy company that went public in 1995. At the time, Omega was the 11th-biggest shareholder of SunEdison, with 8.8 million shares.

It's a large stake, but it is still unusual for Cooperman to pick up the phone to publicly ask a question on a company's quarterly conference call.

These were no ordinary circumstances, however. After enjoying the benefits of a classic Wall Street hedge fund pile-in – when the smartest money in the stock market wants nothing more than to buy, buy, buy – SunEdison was crashing.