You do mean the "Great Health Potion" and not "Great Health Regeneration Potion", yes?
If it still doesn't show up it could be an old bug that is not appearing anymore in the few latest versions. Have you been playing with an old save file maybe?
Viewing post in Potion Shop Schwesterherz version 0.31 Patreon release comments
I'm afraid that starting over is necessary then. And yes, it resets the pictures as well.
In the future, people who played version 0.3 will be able to continue playing with that file for upcomming versions.
If it helps, there is a small public cheat to use once to give the player a better start. It provides coins, potions and more. The cheat is: headstart.