Wait, wait, back up!
Did washing the device reduce/remove the burn in?
No, it was a separate potential issue unrelated to the burn in I was worried could cause my trade in not to go through. I know they typically check for any type of water damage when you do a trade in. I was concerned there could be signs of my phone having been wet several times, even though it still worked just fine.
I was mostly worried about the burn in though. I had left YouTube on while I was driving a lot and on a white or light back ground you could see the layout YouTube had. Even to the point you could clearly see the thumbs up, and downs for videos.....lol