You dont say how much braking you used during your drive. Did you do a lot of braking? If so this could result in the brakes becoming very hot. If, as you say, only one side (driver's side) were hot it may indicate that those brake pads (I am assuming that the car has discs on the front) are badly worn. Therefore I would strongly recommend that you take the car to a garage to have them checked out as soon as possible.