Problem I tells you how to perform a Steam File Integrity Check. If you are missing any files or some have corrupted during installation, that should fix them.
Then load an earlier save of your game, which you should be able to do from the Main Menu > Load Game option.
I checked the game files and the blank note was there. I found the bmp and ent files.
It took me about an hour to get to the part where you need the code.
I'm wondering if the code is 1371 or if it changed.
If it changed, please tell me the new code to section c.
Thanks.
It looks like you have to accomplish the tasks beforehand in order to continue (based on a search I did). Like I said, try loading an earlier save of your game. By doing so, it will reload the map anew and will re-place the objects again.