i was playing in fulloffline mode and this happened:
i had a RAM associated crash, after that crash the fulloffline character was gone.
so i would recommend an implementation where a save copy of the last auto save of the character is constantly kept in an folder- which then can be replaced if there happens something - like a crash. same like for example its done in plugy addon for diablo2.
so you only lose some minutes of gaming and not the complete character