When a company is bought by another company, then all their intellectual property is usually transferred to the buyer. That means when Adobe bought Macromedia, then all the copyrights to all Macromedia products presumably went to Adobe. So Adobe can take legal actions when you violate their copyright on Macromedia Adobe Flash 8. I said "usually" and "presumably", because there might always be some contract clause in the purchase agreement between Macromedia and Adobe which says otherwise. And that agreement might not be public knowledge.
When a company "disappears", then things can get even more complicated.
When a company goes bankrupt, then their assets get liquidated. That means everything they own - material or immaterial - gets sold to the highest bidder. Who that bidder is is not always public information. So the copyrights might land somewhere where you wouldn't expect it. In fact there is a whole industry of "copyright trolls" who buy IP from defunct companies just so they can sue anyone using that IP.
When a company is dissolved voluntarily, then any of its assets either get sold off to the highest bidder just like during a bankruptcy, or become the personal property of the company owner(s). Who might be private people or a parent company.
Sometimes a company might "nominally" go out of business by sacking all employees and ceasing all business activity, but might still exist on paper. That means whoever owns the company could at any time decide to go back into business just to start a lawsuit.
In some cases it might be hard to tell what actually happened to the IP rights to a specific piece of software. The information might be in some contract deeply buried in some file cabinet. Or perhaps there is no documentation at all, so finding out who owns what can become an immensely difficult lawsuit.
Bottom line: Who owns the copyright on what is not public information. Just because you can't find out who currently owns the copyright to some intellectual property does not mean nobody does. And when you violate their copyrights, that person might suddenly appear with a lawyer and make all kinds of demands, including suing you for statutory damages (which does not require them to prove that you actually caused financial harm to them).
