Dating

What should I text back when he texts me "Wish you were here"?

I just started to date this guy a couple of weeks ago. He is very sweet and it seems he really likes me. However, there are times in which he go out with his friends, he didn't invited me (which I understand), but then he texts me saying that he wish I was there. What should I text back? I mean, I wish I could text him: "Well, you didn't invited me.." in a funny way, but I don't want him to think he has to invite me everywhere he goes.
What should I text back when he texts me "Wish you were here"?
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