Does the merchant sell the initial ingredients that are given to you at the beginning of the game? I haven't seen them show up in his inventory, and was wondering is someone else has.
Edit 1: Continued to play, and I found an interesting bug. I purchased all of the potion recipes which caused the next merchant purchase window to be extremely small, and to quickly randomize all of its content.
Edit 2: With the merchant randomizing all of the ingredients so quickly, I tried to find the original ingredients in his store. I was unable to do so; maybe I was extremely unlucky or the original ingredients are not sold by the merchant.