A copyright search and filing papers is not necessary to enforce a copyright. You can put (c) copyright and date anything you created and it is validly copyrighted. Intellectual property is still property. The only hard part is that you have to prove that it was yours first.
I have software, designs, and other writings that I have copyrighted. All you need to prove copyright is proof that you wrote, designed, or published it first. It's nice to have published dated material, but not always necessary.
I have copyrighted material out there that I hsve seen others use. It made me feel good, as in the copyright notice I allowed the use if credit was given and notice maintained. In particular I saw a specialized q=1.85 semi-log graph I had made in Autocad used somewhere else.
I have seen others use my logos or titleblocks without permission. I called them immediately and made them stop. I also let them know how much it would cost them if they wanted to buy rights to my intellectual property.
Heres the real funny thing- if you hire me to design a fire sprinkler system for you, you won't own the design. You only get to use that design on that project. You can't copy it or re-use it without my permission. All those custom homes out there and a lot of owners think they own the design because they paid for it - but it isn't the case.
Intellectual property is really weird - even if you write some program, or paint a painting, or invent something while on the clock for someone the person paying you may not even own the intellectual work that you created. Best to get it all down in writing.
Oh, and it helps to have a family member who is a lawyer.
Chilly