Right, so I met a girl today, we spoke abit Nothing major like Now, she told me her surname, but I only overheard her first name, when she wasnt like talking to me So if I add her on facebook, that's stalkery So what does I do?
Meh, Facebook wouldn't mean much, as long as she told you her name. Just add her saying hi. It would not even cross her mind the think about stalkery, its just Facebook!
And you're not exactly "in a pickle". There are no rules saying that if you know someones name you must add them on facebook. All you had to use was the smallest bit of common sense and you could have had your answer straight away and not look like such a tool.