I saved, but the game didn't save

The title might sound redundant, but it's true. Yesterday I was working on building a lot, saved my game multiple times over the hour or so I worked on it, and then saved one last time and quit. This morning, when I accessed my save through "load game" and start off on the manage worlds screen, I can see the updates I've made to my build. However, when I click on the lot and go into build mode, all of my progress reverts. I don't understand why this is happening, as it has never happened before.

I do use mods in this game, but they've never caused an issue with saving before.