It's not a secret chest. While doing my Apocalyptic Mode play-through, I noticed the location of a soul chest on the floor directly under the Anvil in the broken down building. The same exact spot that I remember there being an indicator for a chest during my normal play-through while using the Fury's Embrace attachment to find all my missing collectibles.
Hope this clears up the confusion over the "secret" chest. There's only three hidden chests. The fire hydrant chest in The Crossroads, the tombstone chest The Chocking Grounds, and the torch chest in The Twilight Citadel.
...I spit on my life. Death in battle would be better for me than that I, defeated, survive. ~Buddha
^ I thought about that... but when I saw it there when dealing with the lurker, for some reason it felt new, like I've never seen it. It might actually only be possible to get during the lurkers. I don't think I've seen it there before that.
Best Buy sucks so bad, I have to Sig it! The customer service were stupid & they lied. Don't Buy from Best Buy