no autosave ? using , <- hotkey will bring it up, maybe you might get lucky? yea it happens i hate it also, but now i make like 2 save files a day to save to and remember to save a lot, its odd but you can't lose work, so i do (name)_(numbers).ztl = example AW4 _1.ztl then AW4 _1.5.ztl - next day is 2.0 / 2.5 on and on.
Good luck and sry but it happens and it sucks.