Depends on what kind of a friend he is. If he is a very good one since a long time I would suppose he is not receiving the messages. If he is fairly recent, I would think he doesn't want to be my friend any longer.
It depends on how many messages your sending, I would be inclined to think they want to make the most of their year abroad, opposed to spending to much time messaging every detail of what their up to.
I've done this and I can only say, guilty!
When I went to US, I got caught up in various things, it's all a novelty and you're having a good time. All thoughts of friends go out the window. Luckily I have very understanding friends.
Sorry, we can't find any related questions. Try using the search bar at the top of the page to search for some keywords, or choose a topic and submit your own question.