(In fact, I know a private collector who has the Wing Commander I Amiga source... but it's not leaving his possession.)
Not even to make a copy for fans to port? or to give to EA?
That wasn't what they did back then, though. Maybe id, but 3D Realms didn't make engines. They didn't even make the Build Engine used for Duke Nukem 3D. There were a few (mostly crappy) games based on the Duke Nukem 3D code, but that definitely was not the primary goal in its development. There are tons of old games that have had either their source code released or recent ports released. Companies keep track of this stuff. Maybe Origin was for some reason especially bad at it, but while they existed, it must have been around somewhere.
I fear you're missing the point, the source for the build engine exists BECAUSE the engine was sold, not because they wanted to sell it - once you do sell it though, it becomes a commercial assett to have neatly, well organised and well backed up code!
Anyway, I'm just finishing up my PhD and during that time have written literally thousands of lines of code - every day before i head home i copy my work folder into a folder labelled with that date and every six months those folders are burnt to dvd.
Yesterday I tried to read a data file I output back in February 2008 - in the interim i've changed my output format, my read in format and even the way i do analysis - the point being that the graph i got out was nothing like the one i was trying to reproduce - but was from the same datafile!
It took 4 hours to find the right sourcecode and even then i needed to modify it because the backed up copy, was saved AFTER the build i used to make the graph, but changed AFTER the previous backup.
The code that can be lost in the course of one day is immense. just because you back up religiously and all the time doesn't mean you won't lose stuff. Those data files are only readable now because I happened to save the sourcecodes from that time, and even then, i could have tweaked something during the day and then changed it again before backup.
The point is that sourcecode is transient at best - if no-one else will ever need to read it (by your logic) then it stays rough and ready and poorly annotated. Given even a couple of years and that source can be lost, corrupt, the disc damaged etc. I fully expect that when i move house in a few months, those dvd of source and data files will become stuck in a file with the lab-books in a cupboard. Maybe one will get scratched? When i move again in 4 or 5 years, it might get dumped in a box and not opened till the next move - when - if it's lucky, I won't just throw it out. Maybe i'll look at the dvd and laugh at the small capacity and back it up onto something new before my now ancient dvd drive dies, but what if that little scratch stops me reading that single section of the dvd where the source code of my program on the 16th july lies - I lose it!
When a project is finished, people box up the posters etc and bin all but one, they back up the data to one device and delete the rest and they move on - if it's an amazing place, maybe they'll keep a copy of the game and the advertising etc. But even the best companies (ken williams at sierra?) can't keep everything - and that's how stuff gets lost. Just because these days people back stuff up relgiously doesn't mean that if you tried to get the model of a fighter from a project your company made 3 years back you would almost definitely have severe trouble (where's the disc for a start!).
Sorry about the rant - but when loaf says it's lost we nod sadly and say, maybe there is a copy out there - we don't moan that it can't be lost because everyone backs up nicely these days.