Also, even if it got lost in the mail, if she was your best friend you would have known before any actual invitations went out. She wud have actually TALKED about it

does this person know that you are best friends?

Just a different perspective: After a 5 year engagement, my husband and I decided it was time. We planned and pulled it off in two weeks, which is pretty in character for both of us. It was immediate family and a few close, local friends. The next morning we changed our FB statuses and were enjoying the best wishes rolling in when one friend, who lived several hours away, threw a fit via the FB feed and text message because she hadn't been invited. We are no longer friends. OP, I know your feelings are hurt and that sucks, but remember, your friend getting married isn't about you. Congratulate them, give it a few weeks, and then talk it out with your friend. Either there is something about the wedding you don't know or (as many have pointed out) something about your friendship you don't know. But if you are a true friend, you will give him/her the benefit of the doubt for now, let them enjoy the glow, and discuss it rationally in the future.

Maybe family only?

Maybe it actually did get lost, benefit of the doubt

Some best friend.

Maybe she/he wan't to give it to you in person?

why did you find out by Facebook if that was really your best friend