So many games are lost in time due to this.
My favourite game off all time, Homeworld, got remastered years ago. Its fantastic follow-up, cataclysm could not be included in the renaster. The reason? Lost source code. No backups, studio got bought, diveded, merged, shut down and nobody thoight it prudent to safeguard that what they bought; the code and ip.
It happens. Often.
I disabled ipv6 long ago and never moved. Not even blinked.