i spend a lot of my time making photograms either in a darkroom
or with the sun. a lot of them are with cyanotype chemistry,
and the rest of them are with old photo paper.
even hand coated metal plates ...
and some times they are done in a camera ..

i have prints that seemingly have not been destroyed in sunlight
or darkness and it happened by accident one day ..

i had some old glass plates that i coated with 15 year old liquid light
and after it was put in the sun i stuck it in DEVELOPER ..
it was my spent old sumatranol 130 .. which has a lot of coffee, sodium carbonate and vit c in it
and a shake of ansco 130 ...
then i fixed the image and it didn't vanish ..

so if you have some spent developer ( not sure if it matters what it is )
it might help save your images ...