Hearing about a party your sibling hosted from a 3rd party...

[opaldragon]

How would you feel and what would you do in the following situation?

Thursday: You call up a friend of yours to say hello, how're you, etc, and he brings up in the conversation if you are going to a party that one of your GLO siblings is hosting the upcoming weekend. You had absolutely no idea that this sibling was hosting a party, but instead say that you're out of the loop. He invites you to the party and says that you absolutely must attend. You promise nothing.
Friday:Later on, you call one of your siblings to say hello, how're you, etc and they ask you if you'll be attending the party. You respond, yet again, you're out of the loop.
Saturday: The party happens.
Sunday: You go to a sibling's birthday dinner and siblings talk about the party and ask why you weren't there. You say that you weren't feeling well that day, and hey, you're out of the loop.
Tuesday: You are in the Student Union, having lunch and hanging out. A friend of yours comes up to you to say hello, how're you, etc, and then asks you why you weren't at the party. You stick to your story.
Other important notes: The house where the party was hosted is a house where 5 of your siblings live. The friend that you called on Thursday is one that you invited to a party that another sibling of yours hosted, where he met siblings of yours, and this is how he was invited to the party in question. The majority of the people that attended this party are friends of yours, and are used to seeing you at parties and functions. The friend that said hi to you in the student union is a fairly good friend of yours. The majority of the people that attended the party in question are members of XYZ GLO, of which you know nearly the entire chapter and are respected and liked by the chapter.