Former options market maker. We regularly got incredibly detailed data requests from regulators following corporate actions. Everyone who made money got scrutiny. Anyone who made money who wasn't similarly profitable before is almost automatically punted to their broker's compliance department, who will put in several hours of investigative work by default.
One of the most consistent knowledge gaps between professional and amateur traders, I've found, is the underestimation of how advanced and pervasive insider trading / market manipulation surveillance is.