If my opponent reveals Tideturner and I use Gust on it in response, does the swap effect fizzle?

Ruling: Yes, using Gust on Tideturner (or the unit it targets) in response will cause the swap effect to fail. The ability will resolve but do nothing.

Sequence:

• Opponent reveals Tideturner and its ability goes on the chain, selecting a target unit
• You play Gust in response, returning either Tideturner or the targeted unit to hand
• Gust resolves, removing the unit from the board
• Tideturner's ability attempts to resolve but cannot evaluate the referential information ("my location" for Tideturner's position, or "its location" for the target's position)
• No swap occurs; the ability resolves to no effect

Nuances:

• Triggers generally don't care where their source goes after being placed on the chain, but Tideturner specifically fails because it contains referential information ("my location", "original location", "their location") that cannot be evaluated when the referenced unit is no longer on the board
• If a unit changes zones to or from a non-board zone and returns, it's treated as a different object and is no longer a legal target
• "Original location" refers to where Tideturner was when the play effect began resolving, and this information cannot be defined if Tideturner has left the board