I have a really similar question because I wanted to try for the rainbow hair girl on my ipod touch, but the spikey haired guy, mohawk guy, blue haired girl, and rainbow girl have never shown up in my adoption screen.
I do not have vf for the computer, so I do not have access to the head chart either, but if the one I found in the forums was right, I currently have 2 hairstyles that are not on it