It was a fundraising like none other: An unusual structure, Goldman Sachs teaming up with two obscure brokerages and the controversial financier, Lars Windhorst, acting as one of the deal's architects behind the scenes.
Investors snapped up the $1.2 billion in bonds that, in turn, channeled proceeds to a cluster of airlines linked to Etihad Airways. Within months, bankers handling the sale were crisscrossing the Atlantic, collecting awards for their creativity.
Two years later, the deal went bust.
A group of creditors is now resorting to unconventional tactics to recoup losses. They've hired a private intelligence firm. The mission: Dig out details into how the deal came together, including the roles played by Mr. Windhorst, the airline and the fundraising group, according to people with knowledge of the situation.
The brewing fight places another unwelcome spotlight on Goldman Sachs Group Inc.'s willingness to raise large pools of capital in unorthodox or risky deals. It also threatens to drag the Wall Street giant into another blowup over its ties to Mr. Windhorst, whose web of business dealings has drawn fresh scrutiny in recent weeks.
"There were a lot of strange characteristics," Roger King, an analyst at research firm CreditSights, said of the bonds Goldman helped sell. "It was a bizarrely complicated deal. A hairy deal no matter who brought it."
One question at the center of the airline fundraising in 2015 and 2016 is why Goldman agreed to fill the breach as another big bank, HSBC Holdings, dropped out, according to the people with knowledge of the matter. Such a large financing probably couldn't be completed without the help of a global bank.
Creditors including investment managers BlueBay Asset Management and Gramercy Funds Management have enlisted the private investigators to help them push for maximum recoveries from the busted bonds, the people said. Representatives for the two funds declined to comment or identify whom they've enlisted.
Their effort contrasts with the typical reason that investors hire corporate spies. Usually, bondholders hire intelligence companies in less-developed countries to track down assets or follow the cash trail, said Robert Southey, founder of Southey Capital, a London-based broker. It's relatively rare to get private investigators to look into deals that involve one of the world's largest investment banks and a major airline group. One significant bondholder has already grown uncomfortable with the tactics, according to a person with knowledge of the situation.
Spokesmen for Mr. Windhorst and Goldman Sachs declined to comment for this story. A spokesman for Etihad said the airline doesn't comment on "rumors or speculation."