Are there any quests from mobs in Mount Hyjal?
In Mount Hyjal, are there any quests that are started from mobs drops?
If so, what are these quests called (links please)?
(I missed a quest in that area... I got 114/115. are there any quests hidden?)
No. Here's a listing of all quests started by an item drop added in Cataclysm. As you can see, there aren't many, and they're almost entirely in Vashj'ir (with a few in Uldum and Deepholme).
More likely, you've missed a hub. I'd suggest trying WoWheads 'personalized search' feature to see which quests in the zone you haven't completed.