Should the authorities get involved?

My mother purchased me a car off of Facebook martketplace a month ago, she got the car and I got to test drive it but something seemed off with the car when driving so we called the seller and he said he’d come pick the car up and take it to the mechanic himself. He eventually comes and takes it to the mechanic as he said and tells us there was that the mechanic said there was an issue with 1 sensor being off. Weeks have passed and he still has the car and calls sometimes telling my mom about how the transmission isn’t good and he’s paying out of pocket for a new one so I’ll have the car soon but it’s been weeks now, and I’m worried it’ll never get it back. She had registered it and titled it, and everything. But I’m not sure if he’s being genuine, and my mom still believes he’ll come around whenever he says he will
Should the authorities get involved?
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