However, there is no officially recognized game called "Pokemon Flora Sky". It is possible you're thinking of a fan-made game or a modified version of a Pokemon game.
To help you find what you're looking for, I need more information. Please tell me:
* What game are you playing? If it's a fan-made game, tell me its full name.
* What is the "Secret Potion" for? What effects does it have?
* Do you remember any other details about the location? Any landmarks, nearby Pokemon, or specific areas?
Once I have this information, I can better assist you in finding the "Secret Potion".