Knightmare Gryphon and B-Buster Drake

[Babycakes17]

Okay, I'm not entirely sure if I can do this, so I'm hoping to find the answer. I have Proxy Dragon in the main monster zone, Summon Sorc. in the extra monster zone, and B-Buster Drake in the main monster zone with no cards in hand. I link away Buster and summon sorc to link summon Knightmare Gryphon, Keeping in mind I have no cards in hand. Can I CL one Gryphon, CL Two Buster and resolve, allowing me to add one of the Union Monsters to my hand and discard that same union monster to resolve Knightmare Gryphon's effect?

[Orphea]

Gryphon cannot be used as it's cost is to discard in which you do not have a card in the hand.

[__Blank__]

It's activation condition of discarding 1 card is unable to activate (Public Knowledge regarding you have 0 cards in hand when it would trigger, so it's unable to activate at all in that scenario).

If you had a card already in hand, and went Cl1 Gryphon CL2 Drake, you could discard the card you add via Drake, this is because you already had a card in hand when Troymare/Knightmare Phoenix was summoned.