For all you know she could be back with her boyfriend. My advice is to send her a text message, calling her out for not calling you back.. since she is 18, you must add an lol or .. like "Jeez, thanks for calling me back ".. if she doesnt respond at all, fuck her.. shes not interested.. if she is at all she will respond and make some excuse what happened, as soon as she does u can tell her she can make it up to u by going out with you this weekend. Just cut straight to the point, especially since you barely know her and trying to make awkward text conversation is painful. I personally hate talking on the phone, so to me texting is the way to go. Make casual conversation after, especially if you don't know the girl that well... try to find out a little more about her before the date so you arent just sitting there staring at her. Stalk her facebook/twitter/instagram. It will tell you more about an 18 yeear old girl than you could ever imagine.
Matty Mate, i have to disagree with just about everything, if it works for you then thats fine, but i would never be passive aggressive to a girl at first, its a weakness, if shes not texting back its obvious shes not interested at all, what made him think there was any interest?? she gave him her number, all girls give out there number and have 500 friends of facebook, she said "i call you later" i say that all the time, i say that too total strangers.
dont stalk her, he will get to anxious or upset if he sees a guy hugging her, i bet its a ugly bitch too, but i do agree on straight to the point in his message if he must. i think the boats sunk though.