When was the last time you played? A month ago? 2 months? A year?
Chances are, that if you have been gone long enough so that you have no idea what is going on, many of the players on your friends list have "moved on." It could be they lost interest in the game, possibly grew out of it. It happens to all of us sooner or later.
I'd recommend just going out there, and trying to find new friends. The game has been throwing out updates left and right, so I'm sure friends you find now won't be leaving for a while
