This may surprise you but even players who play for many hours a day eventually grow bored and quit these types of games. Or simply something in their real life prevents them from logging in, anything from work/school/college to a downed internet connection.

Chances are it's probably nothing and if this Boonini thought more of you I'd have thought he'd contacted you through other means such as Skype or FB. Bottom line is you were just a player in a game to him, in time others will come and go. It's an enriching experience and there will be some who'll eventually become 'cyber' penfriends but most will recede into shadows of the past.