What is the recourse for a undriveable car supposedly bought through you?

Drive the vehicle through their front door . I'm sorry but if you went through legal channels you and I know nothing would be done .

Cargurus is an advertising site only. Similar to Craigslist, Facebook Marketplace, etc. Depending on the Laws in your State you may have some legal rights, but on an eleven year old vehicle, I doubt it. Especially if you bought the vehicle sight unseen and didn't have it inspected before you bought it. If this was a long distance purchase you must go to the seller's location to take legal action. Good luck to you! Jim