I found out that a neighbour and good friend is having a big birthday party tonight and has invited pretty much everyone locally except us. I found out because many of the people who are invited assumed we were going too; I have no idea why we weren't. We live within one minute's walk of them and just drove past the house on our way home. They have a marquee in the garden. It's a big do. AIBU to send a text to say the house looks lovely and I hope they have a nice time when I have severely mixed feelings about it and no idea why we've been left off the list. I do genuinely like them and hope they have a nice time but I also want to let them know that we know we've been left out, so I would absolutely be sending it to convey that message. Should I just leave it?