When player1 uses gust on a target unit that was selected by hidden blade, does the controller of the target unit still draw 2?
No, the controller of the targeted unit does not draw 2 cards.
According to RiftJudge FAQ #5070, for the draw effect on Hidden Blade to resolve, the unit must be a legal target at the moment the spell begins to resolve, and it must be in a zone where the spell can ascertain its information (specifically, on the battlefield or in the trash if the spell itself moved it there).
Sequence of Events
- Player 1 plays Hidden Blade, targeting a unit on a battlefield.
- Player 2 (the opponent) reacts with Gust, targeting that same unit.
- The chain resolves in reverse (LIFO). Gust resolves first, returning the unit to its owner's hand.
- Hidden Blade attempts to resolve. It checks for its target on the battlefield.
- Because the unit is no longer on the battlefield (it is in the hand), the target is illegal. As a result, the spell cannot determine the "controller" of the unit, and the draw effect does not occur.
This is consistent with Rule 359.3.e.12, which states that if a spell checks information about a target that is no longer legal or whose location has changed such that the information is unavailable, that check returns "null" and all related instructions are ignored.