The secret operation got underway late last year. A small army of researchers were told to fan out across China, to cities big and small, to collect documents and videotape the activities of the prime target. The organizers had a hunch that Luckin Coffee, China’s fast-growing challenger to Starbucks and a company traded in the U.S. stock market, was falsifying financial statements to exaggerate its sales. The organizer set out to prove it, deploying 1,510 investigators to count sales and r