Your old save should still be there if you click "load game" in the main menu. The continue button continues on the latest save you've played, not the one that's furthest, maybe that caused confusion? If you press new game, then go back main menu and press continue, it will continue from the new game. Hope that makes sense.

Let me know if that wasn't the case.

It make sense. I am sorry I overlooked Load Game, probably because I never used Save. My fault. Thanks for explanation.

Oh wow, that just made me realise something, our game actually never says "Game Saved" when it saves the game. Like how usually games have some icon that is shown that indicates saving along with a warning "don't close the game while saving" etc. We should have that too. Thanks for bringing this up :D