are you more a acquaintance then a close friend? all because you introduced them doesn't automatically invited to the wedding. also maybe they had a small budget and only invited immediate family.

I brought a guy I had just met to a party where he met a girl I vaguely knew. They ended up getting married and invited me to the wedding. I got food poisoning, so there's that...

Did you introduce them as in you all happened to be in the same place at the same time and you told them each the other's name since you were talking to both, or did you introduce them as in you thought they'd be good together so you set them up on a date? Because of it's the latter, they should give respect to your matchmaking skills, assuming you haven't alienated them in some way since then. If it's the former, your role was fairly negligible. Don't give yourself too much credit.