Emily, This is my opinion only , but you need to wait him out. Don't call him, IM him. or e-mail him anymore. I really don't know why he isn't your stuff, but guys can be like that at times. Guys can also send mixed messages, just like you said when he ran by and waved and smiled and called out to you like nothing was even wrong. My best advice is to let it go and don't pursue, let him call/IM/or e-mail you next and if he doesn't then he is not worth your time. I know that sounds a little harsh and really tough at this time, but I feel it to be for the best for you and your sanity, For example if you keep calling him and stuff and he keeps not responding to you it just keeps irritating you more and more. i know the fear of the unknown is bad as well, but like I said it is nothing you did to get this treatment from him, soi if he decides to play this game let him because he doesn't deserve you.