BM,
My first response to this was "You gotta be kiddin'". Then I looked at a Blue F and noticed the gap in the eye of the single hook and realized that you're quite right. I just think it's a wee bit odd that the Foxes come with a single replacement hook whereas other lures that have a split ring, making it easy to change hooks, don't come with a spare hook.
Anyway, thx BM and others others who posted. Mystery solved