What should be done when a player misses a trigger that specifies a default action?

When a player misses a trigger that specifies a default action, the appropriate response is to resolve the action immediately without using the stack. This is due to the nature of triggers in Magic: The Gathering, particularly those that explicitly state what happens when they are supposed to occur.

Default actions are those that are clearly outlined in the rules of the game and do not require additional decision-making or deliberation on the part of the player. When a player misses such a trigger, it is important to rectify the situation by ensuring the default action is executed as intended because allowing the game state to remain incorrect would undermine the integrity of play.

Resolving the action immediately is consistent with maintaining the flow of the game while ensuring that rules are correctly applied. Other options, such as ignoring the trigger or allowing it to resolve normally, would not align with the principles of fairness and adherence to the rules governing play. Additionally, asking the player if they want to use the effect later would create confusion and complexity that is unnecessary when a default action is involved. Therefore, intervening to resolve the action without using the stack upholds the game's structure and fairness.