Why???

You should ask him why he did not invite you and not even tell you- you shouldn't get angry so fast and ask for a reason, maybe he has a good one. I hope everything goes well.

It sounds as though he just isn't that interested in you. You'll know where you stand when he returns. If he comes back without a nice gift for you, that is a pretty clear sign of where you rank in his life.

Probably he did not tell you because he changed his plans or he knew you would be angry or he doesn't find you interesting enough to tell or he doesn't care about your opinion or he doesn't see you as his partner/gf. Which of the given options is right according to you? What do you think you can do or change from such a distance? If he is there you can not change is if not there is nothing to do for you as well. Ignore it/him, go on with your life and wait and see what he has to tell you sooner or later.