That makes you one hell of a hardcore GoW player that’s for sure @beeflog . I also haven’t ever seen this happen before for GoW. I didn’t realise OLEDs could have burn in issues like the old screens so I was honestly expecting you to reply you play on PC with a really old monitor or an old tv.
I suspect this issue was caused by long game sessions but you haven’t prevented the display turning off after x amount of time of inactivity in the phone settings have you? I would definitely turn that back on if it’s disabled.
I’ve shared the image with the dev team in case there’s something there we can look into.
Unfortunately, there’s nothing we can do for your poor phone 
I am simultaneously impressed by your GoW devotion and sorry for what happened to your phone.