Have you tried checking your actual save game files? An autosave never saves over your saved game file automatically. It is separate file and could possibly be the file you are after? Play > My Parks
Moving to how do I
Relying on only Autosave is dangerous no matter what situation you have. There might be things happening elsewhere on the computer, outside of Frontier's control, that could corrupt the save process. As WingardiumLevicoa said, Autosave should only be a backup, not a primary source of saving.
Autosave is completely unreliable. There have been a few threads about it. Sometimes it just gives up and goes home early, hoping you don't notice. I sometimes lose stuff too and yeah it is frustrating. It pays to live by the old adage, "Save Often Stupid". I'm not calling anyone Stupid, that's just the saying, ok maybe I call myself stupid when I forget to save myself. It's so easy to get wrapped up in a build that's going well and lose track of time.
Yeah I understand your point but how many times in a hour you must save? I remember not saving for like 3 hours (the time when they introdused screen) and suddenly my PC was frozen. After starting the game again even auto save was not ok and I had to start all over again.