Faithless Looting

You draw two cards and discard two cards all while Faithless Looting is resolving. Nothing can happen between the two, and no player may choose to take actions.

"Flashback [cost]" means "You may cast this card from your graveyard if the resulting spell is an instant or sorcery spell by paying [cost] rather than paying its mana cost" and "If the flashback cost was paid, exile this card instead of putting it anywhere else any time it would leave the stack."

You can cast a spell using flashback even if it was somehow put into your graveyard without having been cast.