What happens to a hidden card when the unit it's attached to is gusted away from a battlefield?

Ruling: When a unit with a hidden card is gusted away, the hidden card is put into trash at cleanup (after resolution). However, you can react with the hidden card before the gust resolves to try to get use out of it first.

Sequence:

• Opponent plays Gust on your unit
• You can react by playing your hidden card while still holding the battlefield
• If you don't react (or after your reaction resolves), Gust resolves and removes your unit
• The hidden card goes to trash at cleanup

Nuances:

• You can react with hidden units (like Blastcone Fae) and they will be played at that battlefield
• You can react with hidden spells like Block, but they may not have any effect depending on timing (e.g., if Gust happens before an attack, Block won't shield the unit being gusted)
• Hidden gear cards will be recalled to base when the unit is gusted, but under current rules they work for all battlefields (though this is not intended and will be addressed in new rules before release)