Warning: the game wiped my save data. This is on PC, it's not cloud-related (I made sure to turn cloud saving off), and the game did not offer any kind of warning or indication that I saw. I had just finished collecting 40 points on the current playlist, returned home, switched cars, and exited the game from the menu. I came back later, started the game, and it greeted me with the first-time setup and a new game. By then, it was too late to rescue my data.
It kept my control bindings and some of my video settings, but not the difficulty, audio, or other video settings. In the save folder, all the livery files for my cars were still there. After grinding back through the introductory part of the game (insult to injury), I confirmed everything else is gone.
Whatever they goofed, that is really something in a game where cars are special limited prizes. I'll have to re-motivate myself to collect the 22B. Maybe I'll settle for collecting it later. No McLaren F1 for me, that's for sure.
Now that I know where the save data is, I will keep backups.