I have had this happen to me and it is not fun. I have found in many situations, that if you don't obsess over the loss of your friend and let it go for awhile, they usually come back after a couple of years. This does depend how close you were to the person before your spat though.
Many years ago I had a friend in middle school whom my family took into due to his crappy home life (long story). I liked the young man, but due to my immaturity I would make off the wall comments about his situation, sometimes repeating what my parents, classmates, teachers, etc said about him. No wonder after about a year, he moved on (it didn't help that my parents contacted social services about his situation either). It took me years to understand totally the magnitude of his situation, and the abuses and neglect that he had to endure. It bothers me that I treated him the way that I did. Even though we chat when we run into one another, he has told me that he wants no contact via phone, e-mail, etc.