Recipe Bug

[BruXsa]

Aren't all recipes learned supposed to be listed in /recipes?

Today I bought a recipe called Booze of Flying, thinking I hadn't read it before since it wasn't listed in /recipes.
However, it said I already possess the knowledge and when I tried /recipe Booze of Flying, it says Please specify the name of a known recipe!

So now I've realized there's been other recipes I've successfully learned that aren't listed in /recipes as well. Is this a bug?