RIAA is known to police bittorrent and related sites regularly. They sometimes offer content for download to collect IPs and, when they find one in the US, send such warnings.
RIAA does not kid around. They will track you down and sue you into bankruptcy. I would take such a warning seriously. Use a vpn from now on, Bugsy. Tor is not really secure anyway, as the FBI and NSA have virtually taken over the node network. Also, flush your cookies, as they may have left a tracking cookie on your computer. If you have a backup dating from before the warning, restore to that, to be more sure. Hypothetically, of course.
I suggest using what I use. It's scary, but legit and in five years, nary a problem.
goldenmp3.ru Yes, a Russian site, with a Chinese biller no less. Your credit card processor WILL flag this the first time. The music catalog is good, cheap and they usually find albums for me in less than a week.
Just a suggestion.