I created an account for the sole purpose of responding to this thread because it happened to me too.
I just finished Episode 2 for the second time and I was all set to play it a third time with my third save file when my PS3 said, "Save filed corrupted. Attempting to recreate" or something along those lines. I know for a fact I turned off my PS3 when it was done saving. I'm glad this happened to other people too and it's not just me. My save file also says 167kb and all my progress is gone.
I really hope someone at Telltale sees this because this sucks hardcore and is bound to happen to more people. It's like playing a Final Fantasy game for hours without saving and then dying, losing all that time you put in.