The sooner you get info out the better the results. From the looks of it this guy doesn't have a history of disappearing and his social media interactions have stopped. Hell, I would be concerned also. Did he seem to show any signs of depression in his latest posts? Has he recently given belongings away? Has he talked about meeting a girl? Think about every interaction you have had with him recently, something that may seem small could be a large clue. I hope you find your friend soon and I am lighting a candle and saying a prayer.