When do hidden cards get trashed if the unit they're attached to leaves the battlefield during a showdown?

Ruling: Hidden cards get cleaned up after you lose control of the battlefield, which happens after combat resolves.

Sequence:

• Player can use Ezreal's action ability to recall during the showdown
• The hidden Tideturner remains available during the showdown
• Player can flip Tideturner during that showdown to bring Ezreal back
• Hidden cards are trashed after the combat resolves

Nuances:

• Even though Ezreal can be brought back with Tideturner during the showdown, his "When I attack/defend" triggered ability will not trigger again because those abilities only trigger the first time a unit gains attacker/defender in that combat