There is a known bug where critters carrying the Island Pamphlets that Clyde requests can be permanently scared away or will otherwise disappear. When this happens, unfortunately the critter with the pamphlet won't come back, nor will another spawn with a pamphlet to replace it, so you won't be able to complete this particular quest today. I'm sorry about this. On the positive side, since it is a timed quest there's no big downside to not completing it—the rewards would have been nice but they're nothing you can't obtain in other ways, and incomplete timed quests WON'T prevent you from completing a bear's storyline.
We've fixed this problem in version 5.2.0 by changing the quest definition—it will involve imps instead of critters since imps with quest items shouldn't get permanently scared away. (After taking version 5.2.0, you might also have to wait a few days for the old definition to cycle out of the rotation.)