Folks, on the Steam forums someone just provided a kind of solution that might work.
"I CAN SEE THE CHEST!
once the job is done, dont go to the circle
restart the game, then go, it will appear"
For all of us that moved past that point this week – it’s no use, but it can be very useful for 2 remaining treasure hunts in Series 9 and forward. I will be trying that on Thursday for sure, not to risk another bug.