Jacob’s cabin doesn’t appear on the map for a couple reasons. First, it appears to be capable of moving, as well as disappearing and reappearing. Hurley first encountered it in a different area than Locke and Ben. Eventually, we see a map of the cabin:

Unfortunately, I don’t believe that this map shows enough of the surrounding terrain to adequately get our bearings. It’s nearly impossible to tell what part of The Island we’re looking at.

So with that reasoning, combined with the fact that the cabin was burned to the ground, I think the precise location of Jacob’s cabin will just have to remain another of the numerous unsolved Island mysteries.

But if anyone can make better sense of that blueprint/map, feel free to make a suggestion.