To be clear, here, Guy, and to flesh out Keri's response, because as a former pro photographer and writer this is a pet peeve of mine...
NOTHING published on the Internet is public domain unless the creator specifically states in writing that it is, and you can prove that he/she did so. Which is what your email to the company seeks to do, so good move.
The simple act of publishing content where it is publicly accessible in no way can be interpreted as allowing anyone else to use the content/granting copyright. If the creator chooses to grant lenient republication rights such a Creative Commons licenses, the material can be used under those license restrictions, but even that is not "public domain". There is a specific license granted and you must adhere strictly to the terms of that license.
This applies to all content (written, video, photo, audio, music etc) and to re-purposing and derivative works. The only practical exception for regular users is "Fair Use" which amounts essentially to quoting very small parts of the original - in order to use it in a review, for example. (Other parts of Fair Use include things like use in textbooks and by libraries)
Bottom line: if a website owner didn't create it from scratch, they have no right to republish/use it without written permission from the creator./copyright holder. And the fact lots of people on the web abuse this law won't protect them if they get caught.
I'm not a lawyer. Don't even play one on the Internets. But anyone who thinks the above doesn't apply to them is asking for a world of hurt. Not to mention ripping off the original creator. If you think you're exempt, better have a good lawyer's proof to back it up.
/rant
Paul
P.S. Some works were copyrighted so long ago (and copyright not renewed) that they have fallen out of copyright protection and are actually in the public domain. But we're talking over 100 years and you'll want to have proof before using.