If a player forgets to use Zhonya's to save a unit and a turn passes before it's noticed, does the Zhonya's go to the trash or stay on the base?

Ruling: The player keeps their Zhonya's on their base and continues playing. However, if forgetting to apply the Zhonya's replacement effect was advantageous for its owner, it could be upgraded to a Warning.

Nuances:

• Zhonya's is a replacement effect, not a trigger
• The penalty assessment depends on whether not applying Zhonya's was advantageous to the player who owns it