I 'forgot' to invite someone to a meeting. I didn't think there presence there was necessary, however it turns out that they are quite upset that I haven't invited them. I will now, of course.
However, how could I word it so that, it doesn't sound so awful, other than I forgot.
I think they are playing this up more than I would in that situation, but its not about me, its about them and how to word an email so that they feel valued rather than 'forgotten'.