First of all, the status of the fence must be determined. If the fence was what defined out of bounds, then he shouldn't have gotten relief. Fences or walls defining out of bounds are not obstructions. In that case, any relief would be under Rule 28, Ball unplayable, and would incur a penalty stroke.
If the fence is not the margin defining out of bounds, then he would be entitled to relief without penalty under Rule 24. He must locate the nearest point of complete relief for lie, stance, and area of intended swing from the obstruction. He is allowed one clublength from that point, no nearer to the hole, for his drop area. If the ball, after dropping, rolls more than 2 clublengths or rolls closer to the hole than the nearest point of relief, or rolls back into a condition of interference with the same obstruction, then it must be redropped. If it does the same after the second drop, the ball must be placed where it first hit the ground.
If the ball doesn't roll more than 2 clublengths, and doesn't roll nearer to the hole, then it is in play, and if there is interference with another obstruction, then he would be allowed to take relief under Rule 24 for that second condition.