Final answer:
Micah didn't notice the nachos because of inattentional blindness, which occurs when a person's focus on one task prevents them from noticing other visible things.
Step-by-step explanation:
Micah is best described as missing out on his favorite snack because of inattentional blindness. This phenomenon occurs when a person fails to notice something that is completely visible because their attention is focused intensely on another task. It's not due to a sensory deficit like prosopagnosia (face blindness), nor is it a failure to notice changes in the environment as in change blindness, nor is it due to using an object in a traditional way only, as in functional fixedness.
Inattentional blindness can happen in various situations, as demonstrated in experiments where participants failed to notice a person in a gorilla costume walking through a basketball game they were watching because they were counting the passes between the players. Thus, Micah's intense focus on the game led to his inattentional blindness towards the tray of nachos.