So sorry that this isnt explained better in the game.
When it says the door is locked perhaps it should explain that you should head in the opposite direction.
The game loops through a series of rooms and the locked door is to prevent the player from going to a previous loop and there is no unlocking the door. It locks behind you at the start of each new day.
I appreciate you being excited to play, and hope you give it another shot!
If you have any other feedback I'll be happy to hear it, since I may release an update and attempt to fix any issues players come across.
Thank you for playing and taking the time to write about the experience. Adjusting the game based on your feedback may help other players to better understand.