Does Pack of Wonders bounce cards with the Hidden keyword, or cards that are currently face-down and hidden?

Ruling: Pack of Wonders bounces cards that are currently face-down and hidden. The keyword formatting on the card is an error.

Nuances:

• The card text as written suggests it refers to the Hidden keyword, but this is not the intended function
• Cards that remain face-up can already be bounced by the unit/gear tag, so the Hidden text must refer to face-down cards