What happened in the jail right after the Tucks left?

In 1950, nearly seventy years later, Mae and Tuck return to Treegap in a horse and buggy, looking very out of place. They are shocked to see that the woods and the Foster cottage are gone, and that there are many new streets and houses and stores. Some people joke about how old-fashioned they look as they pass by, but Mae and Tuck ignore them. They stop at a diner for some coffee, and ask the waiter what happened to the woods. The waiter tells them that three years before, there was a big electrical storm that caused a forest fire, and the rest of the area was bulldozed. Tuck asks what happened to the spring in the forest, but the waiter says he doesn't know what he's talking about.