One of the kids is quoted as saying, "If [friends] go to a party, it feels like, why wasn't I invited?" And...uh. Really? Really? This did not seem like time for a major life lesson? Because your friends: they will have friends who are not you. They will have friends who are not your friends. They will go to parties without you; sometimes they will have parties without you. Because not every event is infinitely flexible or infinitely large. Because not every event is for you. You do this to other people. They will do it to you. Life is like that.
No matter how bad your day is, someone somewhere will be having fun. Possibly even someone who cares about you.
No matter how personable you are, some of the world's fun will happen without you. Even some of the portion of the world's fun that has been assigned to your near and dear.
This is the key to having a happy convention, but it's also pretty key to the rest of your life. Imagine how awful it would be to live with someone whose life was a boring or painful slog whenever you weren't around. Imagine how dreary it would be to have coffee with someone whose only joy in their life was your coffee time.
I mean, yes, if you find that the people you think are your friends are never including you in anything and are always doing things that could include you and don't, it may be time to reevaluate your friendship with them. But if you have some friends who went to the movies without you? It happens. Ask them how the movie was. Converse. Tell them about what happened when you went swimming while they were at the movies. More to the point, go swimming while they're at the movies. Adults need to know this. Teenagers need to know it. Little kids need to learn it before they get to the point of being teenagers and thinking that friendship means always doing everything together. And adults who don't address that and who blame Facebook are doing the teens in their vicinity no favors.