Probably not gone. Cursor keeps a history of every file you save, separate from git:
- Open a file that changed, e.g. your main page.
- In the left sidebar (Explorer), at the bottom, open Timeline.
- You'll see entries with times. Click one from yesterday morning to see a diff, right-click → Restore Contents.
Do that for each file the AI touched. Tedious but it works.
Then set up git today, it takes two minutes and means this never costs you an afternoon again. In Cursor: Source Control icon → Initialize Repository → type a message like "working version" → Commit. Do that every time something works. Now "undo" is one click back to any of those moments.
Git is basically save points for your whole project instead of one file.