Missed Opportunity?

I met a guy last weekend. There were definite sparks. That is when I wasn't sleeping (see previous post). So once again I am obsessing. I do this quite well in private, in my head...people around me have no clue. Guess you do now, but I digress. We did not exchange emails or numbers. He could get that info through his brother. But will he? Come on...someone obsess with me. Am I reaching here? I did send a "thank you" email to his brother hoping he would pass the email addy on if asked for.... uggh!! Did I miss out on something? How far do you go to let someone know you are interested without looking like a stalker? Where's the line?