To lecture children, drop him on a child; this is to teach them skills. Lecturing the tribe is just to gather them together.

There's no way to know where to look for collectibles, but just knowing they're there should give you plenty of time to find it.

Do NOT pause to look for collectibles. By doing this, you may lose it altogether. It may take up to a minute or two for the rare collectible to appear. Since collectibles do not appear or disappear while paused, if you are paused at this time, it's gone.