They may have stripped the drain plug - won't tighten up enough to hold the oil. You may find it only leaks when the engine is off - a lot of the oil gets pulled up into the engine while its circulating, so the leak is less, until you turn the engine off.
There is a slight possibility it was overfilled, which can be remedied by draining all the oil and refilling it with the correct amount.
An older car might be leaking at the oil pressure sending unit, which leaks when the engine is running, but the mileage and age probably don't indicate that.
If the drain plug is stripped, you might as well have the shop order the entire pan and gasket set from the dealer and reinstall it.
But as most of the posters have said - you drive it without oil circulating in the engine, you will be looking in junkyards for a used engine and you will still be making payments on the vehicle you can't drive and can't sell.
Aren't cars fun?