I sure can relate to this issue of trust and seemingly little or silly lies. It drives me nuts!
Since it often makes no sense to me, I am beginning (& it is hard work!) to look at it from a different perspective. To take it less personally, and try to understand what might lay underneath the little 'lie'. In some cases, I honestly believe he doesn't consider it a lie and therefore would not understand why I am upset. And in others, when I am sure he knows, I often see it as fear - fear of my reaction, fear of feeling controlled, fear of being vulnerable, fear of being completely known. In those cases, I try to think of what would it take to make him feel safe to tell the truth, not feel fear of any kind. To give room for him to prefer to choose honesty over deception, or ommission.
In this particular case, could it be that he ALSO got a message from this couple, so they are no longer on the list. I can easily see why he wouldn't get into the details of who he invited but isn't coming. These are the sort of details my SO wouldn't give a nano-second of thought to. So in the end, it wouldn't be a lie.
And while we're on the subject of deception - wasn't it a lie of ommission on your part to ask with knowledge of this cancellation? I do this too, and then I realize that perhaps the whole "lie" could have been avoided if instead of setting him up, I was more direct - like "Oh, I heard from XXX, she pinged that they can't make it. Is there anyone else?"
I despise lying with a passion, but I am beginning to realize that I often contribute to its occurence by either being deceptive myself, reacting to the truths I don't particularly like, or having an interpretation of "The Truth" that is not necessarily the 'right' or 'only' interpretation.
For me, it comes down to reframing. As annoying or confusing as this detail is, in the scheme of things, it isn't a biggie. What SO doesn't understand is how something this small can send me down a big fat insecurity tunnel! Learning to let go of the small stuff helps...
