Warband savegames are located in Documents\Mount&Blade Warband Savegames\{name of the mod, or Native}
There's a file called last_savegame_backup.sav, and that might be your only chance, but unfortunately the chance of it being the correct save is very slim. Anyway, copy the file, and rename the copy as something else, like sg08.sav (in which case it's the #9 savegame in the game, sg00.sav is the 1st one). Then load it from the game and hope for the best.