mmarci: If you find a more advanced version of a certain oil or potion, the obsolete one disappears and the only way to make it re-appear in your inventory if you buy the formulae from a merchant or loot it somewhere.
So I need to find the original recipes again? That seems like a bug.
Ryudo47: Once you have made; oils, bombs, potions, decontoctions, you have them forever.
What you do run out of, is the number of times you can use them.
Meditate in the game key letter "N" to replenish your used stock. Just keep the items in your inventory, even if the bottles seem empty, don't throw them away.
But if I've run out and have the advanced version, my inventory stock isn't replenishing. Meaning I'm not getting the upgraded items either since it requires the original item to make.