Proving Creative Commons Licensing of a Work?

Q7U asks: "I recently posted a few Creative Commons licensed photographs from Flickr on one of my websites. I later noticed that one of the photographers had retroactively switched all of his photos from the Creative Commons license to an 'All Right Reserved' notice. When I saw this I went ahead and removed his photo (even though I understand that CC licenses are perpetual unless violated), but this begs the question: How does one prove one obtained a work under a Creative Commons license, should there ever be a dispute between a creator and the licensee? Is a simple screenshot of the webpage where it was offered proof enough? Any thoughts or suggestions would be appreciated."

Re:Other Considerations

[n9hmg]

That theory is not sound. I just read it aloud, so now it is, though it's rapidly turning into heat and disorder.