hi rudeofus
i don't have experience with unfixed dry dark stored film
but i do with dry, unfixed dark stored paper prints ( those made like a lumen print
but as contact prints or photograms, and retina prints / long exposed in a camera )
they tend to turn grey and useless, at least with me even in a dark bag in a box stored in the dark ...
not sure it it will work with film, although i have a retina film-print made with film that turned black the same way ..
not sure what that means, since they aren't images made through " conventional means"
my guess is it isn't the same .. and my poorly-thought-out not-correct-answer
is that maybe the exposure to the sun, uv, blue light room light &c for an extended length of time
and exposure through brute force ... the affect of the light is somehow stored in the emulsion and
even though the materials are removed from the light source ( where they soaked the rays ) ... the effect of the light
(chemical rays of light reacting with the light sensitive emulsion ) continues and isn't stopped if left unfixed.
so ... it light-ages. maybe short exposures ( like normal / conventional camera exposures with tiny amounts of light )
on film ( and enlarger exposures / conventional exposures ) in conventional developer & the methodology you describe would work
because the exposures isn't the same scale ?
a super saturated salt solution will stabilize the image ( conventionally exposed + developed ) until fixer can be obtained as well.
it takes days, not minutes, seconds or hours ...