I unintentionally missed Mass this Sunday because I was expecting a phone call from my wife to pick her up from the station some time before 6 PM. I waited to get the call and then deliver her home and then go off to 6 PM Mass (the last available Mass I was aware of). Alas my wife walked in the door just after 6:30 PM saying why didn’t I go to Mass? I was under the mistaken impression that I would be picking her up. I don’t believe I have committed a sin because it was entirely unintentional.
If you thought you would be picking up your wife on Sunday evening, why didn’t you go to a Sunday morning Mass or a Saturday evening vigil Mass? Unless you had just cause not to go to Mass Saturday evening and Sunday morning, you did indeed miss Mass and need to seriously re-evaluate whether you had just cause.