Have we ever had lost media of this type

Basically all media is thrown out by creators shortly after its made. IP is a way to stop people using a product, it has nothing to do with "business reasons" or anything.

Basically all simulation games and nerd games from the 90s are destroyed and their own publisher more or less denies their existence, the only games that aren't thrown out are ones with mass appeal that are relevant outside the time and place they were created.

In particular the steel panther series is almost totally gone because the development company not only died but its owned by an ip trolling shell.

Probably? There's heaps of source code out there released by hackers that the original companies no longer have. Certain books were lost for centuries. It's theorized that a lot of the Sumerian documents we have were scribal exercises in writing and weren't meant to be published.