General question: Say we have a game state where a player controls a trigger that's normally beneficial, but would lead to a detrimental trigger firing. The first trigger comes up, but the player doesn't say anything about it, and later on in the turn the opponent notices. Assuming that we're past the point of no return on the original trigger (e.g., it was targeted so had to be announced right away) does this lead to a Missed Trigger warning? In other words, do we focus on the full chain of events that could have happened, or only one the initial ability that was forgotten/ignored?

Specific example: Ahab controls a Colossal Whale enchanted with Illusionary Armor (because what else would fit) and a Trained Condor, and nothing else. Ahab attacks with the Condor and the Whale, saying nothing about any triggers. While choosing blockers, Nadine notices that the Condor should have triggered and targeted the Whale, which in turn would have triggered the Armor's self-destruct. So Nadine calls a judge.

We have said that Cheating is still applicable here - you're not allowed to ignore non-detrimental triggers when they happen to be inconvenient. This leads people to assume that if it wasn't Cheating there must still be some infraction - but I don't think this is actually correct in policy. When considering Cheating, we explored the alternate realities stemming from the Condor's ability resolving, and determined that one of them was bad for Ahab. But as far as what's actually happened in the game, he hasn't had the opportunity to miss the Armor's trigger yet. So if we're not bouncing him for Cheating then it seems like the appropriate fix is to issue Missed Trigger: Stern Look, and ask the opponent if they want the Condor's ability put on the stack. If “yes” then observe from a distance and make sure they handle the Armor properly. Or do we actually acknowledge the alternate reality and issue Missed Trigger: Warning?

You would definitely want to investigate, and if it looked like Ahab missed that Condor's trigger intentionally, then he's most likely going to get DQ'd. Otherwise, since the Condor's trigger is not considered detrimental, we cannot award a penalty for Missed Trigger. The recourse is that Nadine, since the trigger was discovered within a turn, can have that trigger put onto the stack now, causing the whale to be targeted, and thus triggering the Illusionary Armor.
Staying behind to observe the Illusionary Armor trigger would also be wise. :)

Confusion on a trigger like Colossal Whale's wouldn't surprise me. Between the presence of “may” and the placement of the word “target” after the “may”, I'd expect the majority of players to think it optional to “trigger” the ability at all. Or that they must choose a target. (Based on the response rates of certain practice questions, I'd guesstimate that better than 80% of the player population believes this.) Even in this circumstance, I'd still lean “misunderstanding” more than deliberate cheating.

EDIT: Apparently, my own lack of familiarity with the cards shows. I was thinking about Colossal Whale and not paying attention to Trained Condor here. (Which requires a target and isn't optional at all.) Mea culpa.

That being said, while the event of targeting leads to a detrimental outcome, the trigger in and of itself isn't generally detrimental. In fact, evaluating the trigger in this specific circumstance based on the potential game state is precisely the opposite of how the policy is worded; we don't want judges to consider the game state in terms of making that particular assessment. (Yes, let it guide your investigation. But that should be enough.) So, while having to choose a target would lead to a potential detrimental, that doesn't make the trigger generally detrimental. It's just specifically detrimental here.

In short, the outcome would still be the same: No penalty, since the trigger is not generally detrimental. The opponent gets to choose whether the trigger is put onto the stack or not; at which point, the player is likely to lose Illusionary Armor.

Edited Brian Schenck (July 9, 2013 01:06:10 PM)

Trained Condor
Creature
Whenever Trained Condor attacks, another target creature you control gains flying until the end of turn.

Illusionary Armor
Aura
+4/+4
When enchanted creature becomes the target of a spell or abitily, sacrifice Illusionary Armor.

Colossal Whale
Creature
Not relevant text for this situation

===============

Since cards aren't in Gatherer yet, please, copy relevant text.

Originally posted by Tom Wyliehart:

We have said that Cheating is still applicable here - you're not allowed to ignore non-detrimental triggers when they happen to be inconvenient. This leads people to assume that if it wasn't Cheating there must still be some infraction - but I don't think this is actually correct in policy.

Just to clear this up:
Missing your trigger is still an infraction, even for benefitial/non-detrimental ones, we just do not step in and/or give a penalty for it, unless it is a detrimental trigger.
From the IPG:
A triggered ability triggers, but the player contolling the ability doesn't demonstrate awareness of the trigger's existence the first time that it would affect the game in a visible fashion.
From the IPG examples:
A. Knight of Infamy attacks alone. Its controller says “Take two”.

The example is clearly not a detrimental trigger, we would not step in, we would not give a penalty here if called, but it still is an infraction ;).

This also needs to be the case, because otherwise, you could never be cheating (by the letter of the book) by forgetting your generally non-detrimental trigger, since for cheating to have occured, you need to have intend and knowledge that you are actually commiting an infraction.