According to every online reference I can find, Material Quest 3 in Xenoblade is unavailable until you have access to Valek Mountains. Because the game gives you access to Quests 1, 2 and 4 before this point, all Google searches on the quest invariably turn up questions from people asking where the quest is before they've reached Valek.
However, I currently have access to Valek Mountains (story-wise, I'm currently in Sword Valley for the first time - see spoiler block for latest plot point), and this quest still will not appear for me.
According to the wiki and other sources, this quest should be given by a Nopon Villager (unnamed NPC) near Riki's House during the day.
I've run around near Riki's house at several times during the day, neither of the two Nopon Villagers nearby will give me a quest (just giving me various fluff talk on Frontier Village when spoken to). I've also tried various characters in the lead of my party and a few different times during the night.
Is there another condition required for unlocking this quest? Is it only available at a very specific time of day that I've missed?
Story progress - spoilers
Having fought Mumkhar in Valek Mountain, I've travelled onwards to Sword Valley where I've run into Dickson. Dickson having now departed, my current objective is to travel through Sword Valley to Galahad Fortress.
Other quests progress
Just to eliminate other options, I'm being extremely diligent with finding and completing quests. I have completed almost every quest available up to Valek Mountain. The two quests I still have open in Frontier Village are:
Medical Advancements, Find the Kingpin
The only other open quests from other areas:
Paola and Narine (Colony 9), Chilkins and Antols (Valek Mountain), Monster Quests 2, 3, 4 (Valek Mountain)
Every other quest should be considered found and completed (asides Valek Mountain onwards, which I'm yet to fully explore)