i recently purchased 400 days, having completed season 1 long ago.
i played through 3 of the little stories, and went off to work, come back and my saves have wiped. no corrupted message, i went to load and there was no saves, nothing in the ps3 save folder either.
interestingly my ps3 was connected to the net, and episodes 2-5 were in the "downloading" section even though i never set them to download (guessing it figured i had episode 1 already), i have them all installed, on the season pass. i cancelled them and went back to the walking dead (still no saves) skipped to episode 5 and pressed play, it started so clearly its still installed so i have no idea why it tired to re-download itself.
my partner also had a save, on my psn that therefore also got wiped, it sucks but we will play again, it's all we can do. I refuse to pay of ps plus yearly just so i can have a backup of the saves - the copy protected thing is retarded, if there is someway you can get rid of that or patch this bug so it doesn't happen again i will appreciate it.