i have had a number of friends go off the skids. i think i too have given others that impression wen i once packed up and left town without a word. my life had miserably disintegrated and i was "outta there."
probably more than guilt, what you are feeling is that you miss your friend. i have several friends who go in and out of focus regarding being online, emailing, or communicating with me. as people grow up, sometimes they leave the internet and get it on with life around them, so to speak. sometimes you have to. there is no free checkbook. get used to the idea that people have to work and have a career.
i have also had some friends flat out reject me. and this is after we were very close or worked together creatively. some people are petty underneath it all. well, that is life. part of growing up is all that sleep-over good-times hang-out mentality definitely gets thrown into the crusher machine. inevitably, people bond with one other person or become loners because they need quiet, and when this happens, it is goodbye and "see you!" to their previous basket and bunch of friends.
May God bless you and keep you, my friend. Find something you are interested in and work hard to get there.