Ah, thank you! I had found scans of complete map sets online (but haven't used them!), so I got to wondering if there was an issue - thanks for the clarification!
The complete maps were probably from the cluebook, which was sold separately. It's included among the extras with the GoG download, so if you get stuck just look up the complete map and the walkthrough there. Even if you don' want to use the clues, it still has some nice lore, although with minor spoilers.