On a technical point, even if the company has ceased to exist, its assets might have been sold, or it might have assigned its copyrights at some point, or perhaps a third party has a copyright interest, and there would be no way for me to know about that.

The broader point to make is that this is a general policy of mine – I deidentify all software that I discuss in any of my RE writeups. Having a blanket policy avoids needing to make ultimately arbitrary decisions about what to name and what not to name – and in any case, not naming the software doesn't prevent anyone from reading the writeup and taking inspiration from it if they choose.

Many companies don't just cease to exist, but rather the rights to their IP are purchased. Some of that IP is viewed as not valuable and ignored... but they still hold the rights to it.

In some cases IP like this can be even more dangerous because there is some disgruntled CEO potentially sitting around with ownership of all the IP and he/she sees you're infringement as a quick cash grab.

Some other company or individual could have bought their IP portfolio and now own the rights. They have no obligation to publicize this, as far as I know.