Two Plus Two Older Archives - potentially counterfeit travelers checks

I was selling a car on AutoTrader...guy emails me, wants to buy my car, asks some questions, we e-mail back and forth, etc. Then he wants to send me a Cashiers check for $15000 for a $7000 car, and send him back the rest. Being young and dumb I say "OK" and dude sends me check from First National Bank on Fla. I go to that banks website (wanted to see if it's legit) and right away I see a thing about counterfeit cashiers checks from their bank. I took it to my bank and they looked at it and said it looked real and had everything they check for when looking for counterfeits. National Bank of Fla says call the FBI if you have a counterfeit check. So I call the FBI. FBI says call the Secret Service, they handle treasury. Secret Service says under $50,000 they dont care, call local PD. Local PD says Africa isn't in their jurisdiction. So I got a $15,000 cashiers check laying around. Tryin to figure out a way to cash it and not get screwed.