We get so used to looking at our plants, sometimes changes just pass by our eyes. The chances of it growing that spike overnight are... well, pretty darn slim to none. But don't feel bad you missed it before - enjoy that it's there now! And that you didn't accidentally break it off because you didn't know it was there :-)
My Mtssa Golden Spider "Copius" did the same thing last year, I think we get so used to seeing the plant we don't notice the spike until it get bigger, your spike was just hiding from you to give you a nice surprise. Great job.