Since the game is over a decade old, if your file is truly gone, many players download a "Chapter Save" to get back to where they were.
Older games may not fully support modern OS, leading to issues with file permissions. If you'd like, I can: Show you exactly where to find the file on your PC. Help you find a community patch for the PC version.
If you are on Console (PS4/PS5 or Xbox), your cloud save might be older than the corrupted local file.
Consoles are more restrictive, but you still have options if you catch the error quickly.