Normal procedure would be to sell or otherwise transfer ownership. Sometimes, when a large amount of intellectual property is involved, a successor company of some sort will be set up to handle the material.
Can't seem to do a search right now, but you might want to try a search for "abandoned copyright" or similar at www.copyright.gov.
When a company folds, it does not mean their copywrited materials become public domain. It and intellectual property rights is normally passed on. Bankrupcy can be anther scenario altogether. Shutting doors or becoming inactive does not mean a company has ceased to exist--all it takes to remain alive is a filing. If you do not find your answer at the gov site try Findlaw it very well may be there.
The copyrighted materials might be licensed to the corporation by individuals, so be wary of using such materials without clarification. The materials could be "works for hire" where the creator retains residual rights.
The cessation of corporate form isn't the same as the dissolution or loss of property rights. A corporation is a legal fiction, usually created to gain advantages under State or federal law. When a corporation becomes a nullity property that was pushed into the corporation generally reverts or converts - it doesn't just disappear.
You need to know a bit more about the wrap-up of the corporation to know about the distribution of rights.