Night shift checking in.
I was able to determine there are no out of sRGB areas in pain.png.
Used Nuke like these guys did.
https://photo.stackexchange.com/questions/92208/how-to-check-if-there-are-any-out-of-srgb-pixels-in-an-image
That image still reaks of stenography. 1125x2436 and lossless uncompressed format.
Don't have much time for stuff like this but will stay at it and keep you posted.