To be honest... he went, yes, but went dateless, when a lot of guys would have found a "girl friend" to go with and have a good time (purely as friends, don't get me wrong). I think anyone would be pretty sad that their bf/gf didn't want to go with them to something like this, and given that it was somebody else, and not him who said it (unless there is any proof he was bitching about you all night or something), I would just leave it as it is.