No worries! It can take up to 24 hours for an egg to be fertilized. From there the embryo needs about a week to work from the ovary through the fallopian tube and get to the uterus.
The term thagomizer was coined by Gary Larson in humor, in a 1982 Far Side comic, in which a group of cavemen in a faux-modern lecture hall are taught by their caveman professor that the spikes on a stegosaur's tail are so named after the late Thag Simmons.
The spiked tail of Stegosaurus (Wikimedia Commons). Way back in 1982, a famous Far Side cartoon depicted a group of cavemen clustered around a picture of a Stegosaurus tail; one of them points to the sharp spikes and says, Now this end is called the thagomizer...after the late Thag Simmons..