Hello,
You haven't accidentally started loading an older save have you? One that's progress is far behind your most recent save?.. I don't personally own the game, but it if allows manual saving, I would select load from the game menu and load an older one to see
where its at in game progress. If it does not support manual saving/loading and only uses an auto save feature, it's possible that the game was started over and the auto save is now based on a new game progress.
A save wont just disappear unless A) It was deleted B) It was corrupt and the game cant load it. C) Auto save was written over by new game. I would also ask to make sure that you didn't start saving to a USB or cloud storage as then you will have to tell
it to save to that new location as well as load from it.
Anyways, let us know, I know it will suck if you cant get the save back, though from what I have heard is the game is fairly short and hopefully not too much trouble to redo your progress again.