Or was "yes, yes, we'll add a story to the backlog to add it to the specs" and it just flat out got forgotten. I've seen this happen so many times where I've been the one to raise the issue and because I've passed it off, I've forgotten about it only to circle back around 2 months later when someone says "Oh, we need to do this" and I say "I raised this 2 months ago, I thought X had put it in the backlog."
And when you go looking, sure enough, there it is in the backlog down in Priority "We'll get to it when we get to it, after all these other more important things that needed to be completed by last week."