If autosave.win.bak doesn't contain your session either, try to recover as soon as possible the most recent (and biggest) autosave.win in ..\Opera\Opera\sessions directory using an undelete program (e.g. Recuva).
If autosave.win.bak doesn't contain your session either, try to recover as soon as possible the most recent (and biggest) autosave.win in ..\Opera\Opera\sessions directory using an undelete program (e.g. Recuva).