I need to get the baldric, but the cupboard it's located in is locked. The key is not in the drawer in the same room - it's been some hours but I believe I found the cupboard key AND used it on the cupboard at the very beginning of the game, when first escaping the jail. Will have to start a new game.
EDIT WITH NEW INFO: I did a fresh play through and I seem to be able to get the key and get the baldric in the first time escaping the jail. I believe I did this in my original play through as well, meaning it must have disappeared from my inventory at some point, but this time I will leave the key there until the point where I need the baldric for story progress. Will report back to see what happens.
EDIT 2: On my new saved game I reached the same spot. Despite leaving the Cupboard Key in the drawer, I cannot interact with the drawer at all to get the key and open the cupboard.