I think typically it just gets misplaced, not lost :-)
I bet it still exists in a lot of cases, but
everybody's forgotten exactly
where
I respectfully disagree. Once a product reaches end of life, it is disposed of.
Unlike entertainment products, which can be resold to the next generation, old
software has been perceived as having no commercial value and is discarded either
to avoid its availability for legal discovery, when a company is sold, or when they
need the space or get tired of paying storage costs for it.
I was hoping that working as the software curator at CHM would open more doors
for finding old software (esp sources). It has not, with a few notable exceptions
like HP. The stuff REALLY is gone.
The main source now for old software are the people that worked on it, who kept
copies outside of the company they worked for.