I need a Hero(ic Trigger)

Andrew and Nigel are playing in a PTQ. Andrew has a 4/4 Polis Crusher and Nigel controls a tapped 2/2 Staunch-Hearted Warrior. Andrew moves to his combat phase and attacks with his Polis Crusher. During the Declare Attackers Step, Nigel casts Savage Surge targetting his Staunch-Hearted Warrior, to which Andrew says ‘OK’. Nigel then untaps his creature, pushes it toward the Polis Crusher, looks around and finds a die, searches for the 2, and says ‘block’ as he puts the die on his card.

Andrew calls ‘Judge!” and explains to you that he thinks that Nigel missed his chance to resolve the Heroic trigger on Staunch-Hearted Warrior.

What do you do? What is the appropriate infraction, penalty and fix?

Judges, feel free to discuss this scenario on Judge Apps!

Answer
Thanks to everyone who participated in this week’s Knowledge Pool! Everyone correctly identified that this is a textbook example of Out of Order Sequencing, but let’s examine the situation (which may soon happen at a Sealed PTQ near you!) more closely.

The definition for missing a non-detrimental trigger is as follows:

A triggered ability that causes a change in the visible game state (including life totals) or requires a choice upon resolution: The controller must take the appropriate physical action or make it clear what the action taken or choice made is before taking any game actions (such as casting a sorcery spell or explicitly moving to the next step or phase) that can be taken only after the triggered ability should have resolved.

Here, Savage Surge untapping the card is clearly a game action that can only occur after the point when the heroic trigger should have resolved.
However Nigel, having clearly demonstrated awareness of the heroic trigger, is resolving the two different actions in an improper order. This fits the definition for OoOS:

The Out-of-Order Sequencing rules (MTR section 4.3) may also be applicable, especially as they relate to batches of actions or resolving items on the stack in an improper order.

Nigel is allowed to put the counters on his creature and no penalty is given. If Andrew still wishes to intervene (such as trying to tap the Warrior again before blockers are declared) then the whole stack should be resolved one effect at a time in the proper order.

Despite this appearing to be a missed trigger at first, OoOS means he isn’t actually guilty of GPE- MT.
Nigel did not place his counters on at the exact moment he should, but whilst we expect players to play accurately, this level of detail can be frequently overlooked and should not be unduly penalised. Out of Order Sequencing allows a degree of leeway in resolving a series of actions as long as it is clear that the player had demonstrated awareness of all of them. OoOS should not used to retroactively resolve a forgotten trigger.