So after being in my lair for a while, I've come to this conclusion:
INFP hide an instance when they are hurt. INFP do this because if they show they are hurt, then others will potentially be hurt by that display. INFP fear this sort of response, because they are so empathic, and if an INFP causes someone else to hurt, the INFP feels even more hurt than the other feels hurt.
So it's like a ricochet process. Early in life, an INFP learns how this process occurs through conditioning, and as such avoids all conflict and all displays of negative feelings if possible.
Would any of you say this is a logical way of viewing the tendency?