On October 20, 2020, I met a fund manager in a course. I was very interested in funds and XAU/USD trading, so I exchanged WeChat account with each other. After he invited me into the group chat, he asked me to invest 6000 first. But I was removed from the group after sending him money, and I was also blacklisted by him, what should I do? Although 6000 is not much, it really makes me feel very angry