As above, but if you don't have the dead lamb, there are a couple of other things you could try. Ewes identify their lambs by smell as well as by call and by sight. Take some of the ewe's milk and rub it over the lamb's head, and take some of the poo from the lamb she already has and dab it around lamb's bum. Milk the ewe into a bottle and feed it to the lamb, so it's own poo will soon smell like her present lamb.