Okay... Now that you mentioned multiple items, I shit you not I got it first try in like a single minute lmfao!
Cool narrative but it ends quite abruptly saldy :/ only so much you can do in a single week, good game, without this hint I would not have found the answer to the puzzle haha.
The camera and the door without a handle + last cutscene made for quite a creepy psychological horror game. Reminds me of the swampman tought experiment!