okay, well first off, don't use Automatic Bone Weights
I guess you can use it for a rough draft, but not only does it do a poor job on finding geometry that isn't directly connected to other pieces, but the weight painting it does is awful.
I highly encourage everybody to not use it..
Anyway, since you did do it and you're still learning, you can just keep going for this model. (if you want)
Make sure to weightpaint all of those little verts that don't seem to be connected at all to the bone you want.