The chest is hidden back in the upper-right corner, under a tree. It will be partially hidden in the grass.
There is one way for it to not show up, and that's if you go to the rebirth fountain, restart the game, and then walk straight up toward the opening. This is because the chest is spawned when the player walks through the trigger, which is a huge like 80-meter invisible sphere that ends just before the Zhidan exit, so there is a narrow pathway between the health fountain and the chest that you could walk through without touching the trigger. Go to magic vendor, then walk back towards the widow--that should guarantee you hit the trigger. It was an oversight. At the time I made a mental note to increase the size of the trigger in case someone entered Zhidan from the exit (say they forgot to activate the city waypoint). However, I was not smart enough to write it down, and I was in the middle of testing and fixing the quest steps, so it was forgotten.
If walking through the trigger isn't working for you, then someone can take a look at the quest file to see if there's an error in the conditional logic. It's pretty solidly setup.
I don't have the working files, but the chest spawn should be working like this:
So, the only way for the chest not to spawn is if you sidestep the trigger (must come through Zhidan exit, or straight from rebirth fountain to do this, or if you talked to the widow on accident, or opened the chest without realizing it.
When player hits trigger
If player has PARCHMENT in inventory
And If player does not have token(LootedChest)
And If player does not have token(GotResistances)
Highlight Widow as QuestDuder
When player talks to Widow
If player does not have token(LootedChest)
Give player resistances
Close Quest (no resistances, just the closing exp reward)
When player uses WidowCHEST
Give player token(LootedCHEST)
If neither of those things happened, then there must be a problem with the conditional logic, or it's possible there's something on the map that can spawn and block the chest from spawning, or I dunno what.
Edit: also, the chest is locked by spawning an invisible squirrel that prevents the chest from being opened (but not from being visible). Oh, and it's possible that I may have missed one of the important refire conditions, but I did test many times after game reloads, etc.. Like, have parchment, run through city, don't talk to lady or touch chest. Exit game. Return to area, etc.. Had no problems. Did not test multiplayer.