There's a man in Fallabur town who will re-teach a Pokemon a move for a heart scale. But you must find a heart scale, they are in several places on the map but are mostly in or near water.
1) catch luvdisc 2) thief from luvdisc Note: I usually go ever grande city to super rod for heart scales. It may not always have it, but there will always be luvdisc there with heart scale. It is...