not to say it is impossible but if it was just fixed unless it wasnt done by a reputable shop I doubt it is the head. If it was done by a shop it should be covered if the repairs were just done this march and it is the head, my suggestion would be to find out where the leak is coming from, could be a bad hose, bad heater core, bad radiator or a few other things and Im guessing it has leaked enough antifreeze out that it is not transferring through your heater core thats the reason your heater isnt working. what ever you do dont overheat the motor this will cause a bad head or head gasket that will not be covered under previous work