Sean did not respond to Liz’s letter because he never got it.
Liz and Sean are in love, senior in high school style. Liz and Sean often fight about whether or not to have sex. They do seem to want to, but Liz is worried. She decides to take her teacher’s advice and go for a hamburger, which does not really work. After a particularly bad fight, Liz writes Sean a letter on the back of a place mat. She is upset when he never responds.
Liz’s best friend Maggie talks to Sean about it on Liz’s behalf. She calls from a pay phone.
“I know you two had a fight, but you could’ve answered her letter and told her…”
“The letter she left in your mail box two Saturdays ago, written on place mats.” (p. 77)
Sean hangs up, because someone seems to be listening in. Sean realizes that it was all a misunderstanding, and rushes to find Liz. He tells her he loves her and can’t live without her. They eventually go all the way, but it does not end well. Liz gets pregnant, has an abortion with complications, and does not graduate. She never speaks to Maggie again.