You must have 2 Fusion Material Monsters in YOUR Graveyard otherwise this card’s effect will disappear when flipped.
If you have Fusion Summoned 2 Fusion Monsters during the course of the Duel, you may return 1 Fusion Material Monster from each of them with this card’s effect. In other words, the returned Fusion Material Monsters do not need to be part of the same Fusion.
Netrep Rulings:
Fusion substitution monsters that were used in a Fusion summon may be returned to the hand through the effect of “Supply.”