when you go to ~/Library/RenPy/ on your computer, do you see a folder for this game, and if you do, can you tell me whether there is save data inside? there should be a persistent save file that includes the save data for what endings you have seen.
hmm, unfortunately I'm not sure why. do the two files in the 'persistent' folder look as if they have been created around the same time that you played this game?
one suggestion I can make is to have a folder called "Ren'Py Data" in the root folder where the unzipped game folder is, and renpy should automatically save the save files there, but that won't bring back the saves you've lost.