Investors on the SBCFX (Xingqiao Capital) platform lost everything in a sudden gold-trading blowup, and the company's Hong Kong office is now abandoned — a heavy loss for thousands of mostly Chinese retail traders.

• On the night of Aug. 19, the platform's automatic trading system fired off huge bets against gold in a matter of seconds.
• Gold then shot up, wiping out those positions — some accounts went to zero, and others ended up owing money.
• Between 2,000 and 3,000 people are thought to be affected, many of them investors from mainland China.
• Angry investors and police gathered at the firm's building in Hong Kong's Central district, but the office had been cleared out and promised talks never happened.
• SBCFX had marketed itself as a licensed international platform trading currencies, commodities, indices and crypto.

Outlook: With the company gone dark, investors face a long fight to recover anything, and Hong Kong regulators are likely to face pressure to explain how the platform operated.