Song about a friend you may not see again?

I have a friend who left a little while ago to go overseas. Because of where we are in our lives, I'm not sure if I'll ever see him again. Right before he left he told me how much he cared about me. I wish that we could have had more time together, but I'm grateful for the time that I did have with him. He is my best friend, and I hope that someday I'll have the chance to see him again. I'm the type of person who likes to get my feelings out through music. I was wondering if anyone knows of a good song? Thank you! :)