Can a buy here pay here lot repossess your car?

Yes, and in South Carolina they can do it without going to court first. The lot holds the title until the loan is paid, and your contract gives it the right to take the car back once you're in default — which your contract defines, sometimes as a single missed payment.

What they can't do is breach the peace. That's the legal line in South Carolina: they may take the car from a driveway, a street or a parking lot, but they can't break into a locked garage, cut a chain, or take it while you're standing there objecting. If it turns into a confrontation, they're required to stop and go to court instead.

Buy-here-pay-here repossession tends to be faster than a bank's, and the GPS or starter interrupt device many lots fit is exactly why. There's no need to send anyone looking for the car.

After a repossession the lot will normally sell the car and can pursue you for the deficiency — whatever the sale didn't cover. If you're going to be late, call the lot before the payment is due rather than after. A lot that's expecting your call has a reason to work with you; one that's been avoided for two weeks doesn't.