You should never, ever, ever, rely solely on auto/quick saves for your games, ESPECIALLY content-heavy RPGs. That's just asking for something to happen to them.
Don't get me wrong, it's okay to use them, they're there for a reason. But you should periodically be making an actual save.
Amen--don't know why people play like that. Aside from autosaves, which I allow, I save every game manually, and 95% of them I rename into something recognizable to me so that I can look at the name and know exactly where the game was saved. Trying to play without manually saving is, imo, just asking for problems just as described here. The save-game function is very flexible and powerful, but not if you don't use it, eh?...;)