Did you encourage that each time it was brought up prior to that day?And if you missed that, you probably missed the bigger event from Spencer's ending.
I don't remember that ever coming up the first time I played his route. Granted it's been months since I did it, but if memory is correct I can't believe I had failed the route to best ending so early on.
I know for sure they talked about it when Spencer was trying on his tux. You're given the option to weigh in on it.