You can stop worrying, and move straight into... whatever it is on the spectrum from hangwringing to panic it is you are looking for, I offer no judgment here... because loss of source code and all build artifacts is the norm, not the exception. Completely normal. Unfortunate, but completely normal.
reply> Worrying because it could mean that the current owners don't even have access to the source code anymore, and it's sad to see the source of those games lost to time.
replyThis is way too common. It even happens to the best and largest games - the code for CnC Tiberian Sun and Red Alert 2 is supposed to be lost to time [1].
Often times it's just IP rights that get passed on when a studio collapses or gets bought out, and in other cases source code for dependencies (e.g. music or video player SDKs) isn't available any more.