A few weeks ago I received an evite for DH and me for a going away party for this Friday in honour of the parents of a girl in DD10's year at school, who are moving away. The mum in particular is lovely and very popular among the mums in the year. I was a little surprised to receive the invite - it wasn't sent to all the parents in the year - because as I said I like the mum, but I wouldn't have considered us close friends, certainly not as close as I know a lot of the other invitees, and the host, are.
To be honest, I suspected the invitation wasn't meant for DH and me at all but rather for another couple who have names very similar to ours - the dad's name (first and last) is exactly the same as DH's, and the mum's is one letter off mine, although the other mum and I don't have similar e-mail addresses. (It has happened in the past that I received an e-mail invitation that the sender quickly realised was meant for the other mum and rescinded! I wasn't upset at the time as the sender was a friend and she was very apologetic and embarrassed.) The other couple weren't themselves on the list of original invitees, so I don't think both couples were intended to be invited. I don't know how close the guest-of-honour and this mum are.
Anyway, I just couldn't think of any way I could ask the host if I was really the intended recipient without sounding ungracious - is there a way? I thought of asking other friends who were invited but again, I didn't really know how - everyone is just so polite I wasn't sure I trusted them to tell me the truth even if it was a mistake. I also never had the opportunity to ask any of them as we never saw each other before I had to decide whether or not to accept, and it wasn't something I wanted to ask by e-mail or text. On impulse I decided I was just being silly and accepted the invitation.
Last week the host e-mailed everyone invited to solicit catering contributions, and I looked for the other mum's name to see if a mistake had been discovered and she was added later. She wasn't so I felt relieved and started looking forward to it. But I found out today that in fact she is going to the party. I don't know any details but it has to be the case that she was invited later than everyone else, so it must have been to correct a mistake the host originally made in leaving her off.
Now I really feel an idiot, and wondering whether I should just come up with some excuse not to go. I'll never get anyone to confirm what happened, everyone will be super-polite and friendly (these people are not monsters) but I will wonder with every single interaction whether people know that DH and I weren't really intended to be there.
Feels like high school all over again. 
Needless to say I've NC'd.