Corina,
Contact the girls that you do have information for. More likely than not, they will have the contact info of the girls that you are missing.
Either way, I don't think you need all 18 girls right now. What you need is a core group of about 10 who are willing to do the "heavy lifting." Once the group gets organized, you can start advertising and the rest will come--plus others you may not even know about!
Don't stress out! You're doing fine.
