Have you made it all the way to the end? Unfortunately, you fell through the map so I am not sure how that happened. Never happened to any of my tests. So heres how you complete the game if you ever want to try again as going past the shaft, theres only 5 mins of gameplay left and arguably the main portion of the game.
once you aquire the first key and crouch through the shaft back to the main hall, you can open the door next to the one you have aquired the hammer from. Thats where you should look for secret passages. If you find that the rest of the game has no puzzles anymore but should hopefully lead you to completion.
again I apologize, this is my first game and despite of doing multiple tests with couple of friends, I havent had glitches like that happen.
if you ever happen to give it a shot again, please do let me know what you thought of the entire thing :)