Yes, but in many cases it is impossible to know who has the rights. The company could have sold the IP, could have transfered it, or perhaps it had multiple owners or even the company was using it illegally! This could create sort of a chilling effect, where people are afraid to take chances because someone might own the copyrights and come back to sue. That's why the copyright system really needs to be reformed. Copyrights should have to be renewed every 7 years or so for a small fee. If you're making money from it, renew it and you still have the rights. If it's no longer profitable or you have no desire to keep the copyright, don't pay the fee and it becomes public domain. This should keep the big companies happy because they can keep their successful IP for a long time like they do now (and a small fee is nothing if the IP is really profitable) but also allow more works to enter the public domain for remixing, adapting, and other creative uses.