Could be from the heater in/out nozzles at the bulk head. The heater matrix is an aluminium affair and very delicate. Not using the right coolant leads to the aluminium nozzles corroding away to the point that the heater hoses have nothing to grip on to. The other place you may have a leak is in the heater matrix itself located inside the car. If that is leaking, the carpets will be wet. Your car has rubber foam backed carpets, so the carpets have to be lifted to see if there is evidence of coolant under the carpet.
Engine related coolant leaks are easy to see, there is the main top and bottom hoses and the smaller one to the expansion tank. I think your car may or may not have a transmission cooler. If it dose, it will be a good idea to check the colour of the transmission fluid. Milky colour indicates that coolant is leaking into the transmission. Beyond that, though unlikely, the coolant bottle is cracked.
The last thing is a leaking head gasket, but this is accompanied with other symptoms. My bet is on the heater matrix.