What should i do about this guy ?? Help?

[Detailed Vision]

I met this guy once and both of us felt instant attraction, after i met him i had to travel to another country, but we still talked on FB , we've talked for 4 months online after we met and we were both so into each other, we have the exact same taste in music and art and everything!
Last month he stopped talking to me all of a sudden or saying hi at all, and since i never really used to start convo with him ( he always the one who starts them) i didnt try to talk to him, one of our mutual friends told me that the guy started seeing a girl we know,,, but he didnt mention anything on FB about it or even let his photos with her appear on his timeline, so hes kinda hiding it, he knows that i might go back home any day, i've already told him that.
so I'm confused should i send him a msg, ask him how he's doing, or should i leave it until he talks to me again???

I don't wanna go back home and find him seeing someone else, and i really don't wanna lose him
and btw i might have trouble going back home right now, it might be for another two months..