Of course, the film was developed – if I remember correctly, in Atomal. It just wasn’t fixed. Post-fixing won’t help now, as the film has already seen the ‘light of day’...
Of course, you can re-fix it. Under the influence of light alone, without subsequent development, the silver bromide converts to silver only very slowly; the speed (if you can call it that) is several thousand times lower. If the negatives were stored in reasonably light-proof conditions, you might even end up with negatives that have not suffered any significant damage.
