I socialise with a group of women in a sport I do, we're on the same team. We don't actually get to play often but we all get along. I really like them all and thought it was mutual and we do get together socially from time to time.
I found out one of them is having a big birthday in a few weeks and going to a concert in a nearby city to celebrate. I also happen to have tickets to the concert, which sold out some time ago. I have found out that the rest of the team were invited to go along together for her birthday. I was not invited. Some of the team now know I'm going along too.
What do I do? Hope I don't see them? Ignore them? Make a point of saying hi? It all feels very awkward. They're not super close friends, but clearly I'm not in the inner circle. The venue isn't huge so there's a high chance I'll bump into them.