Oh, Dear: this is not stalking BUT YOU WERE KIND OF CLOSE! Stalking is a serious, legal word, a felony punishable by law. Stalking is a repeated harassment or other forms of invasion of a person's privacy in a manner that causes fear to its target. It includes such acts as:
repeated physical following;
unwanted contact (by letter or other means of communication);
observing a person's actions closely for an extended period of time; or
contacting family members, friends, or associates of a target inappropriately
Of course, there is cyberstalking as well but the key word here is PERSISTENT ACTIONS that might induce fear in VICTIM. C'mon: that guy is not a victim. Well, the positive thing about this event is that you have to learn to detect when someone does not want to talk to you. If a person blocks his/her instant messages, please, understand that no explanations have to be demanded... wait for the explanations but do not force people into it. Such rude action is not worth a neuron spent on him / her.