I was in the middle of the Sharga ruins level 2, and saving my game, when suddenly I get a message that says "unable to save game" and my save file just disappears. I tried saving on different slots, but I get the same message every time. I have ONE other used save file slot that I am NOT going to risk getting deleted (its an emergency save I use in case I find myself in a risky situation).
I have just quit the game and I'm a little worried about opening up the game and seeing whether it will happen again (Unsure if my save file is permanently gone or not). What should I do?

UPDATE: Just opened up the game, my main save file is deleted, but I can still load/save games.
Is there anything I can do in case the game deletes one my files and refuses to save?