Why can't I revert my theme?

[Android Central Question]

I have an LG G6. There was a phone update do for a couple weeks and I finally got around to it. I had my apps in folders alphabetized alphabetically and my theme fit exactly how I wanted. After this update, though, everything is gone that I have organized and I can't seem to change the theme back to the way it was. Is there a way to do this that I'm missing or what?