Technically public domain means that you waiver your rights to the material in question, that means that everyone owns it now, I'm afraid, but to my knowledge its legally impossible to take that right back.
Really good, hope to use it in Scene 5 in Episode 15 of Ad Astral – The Patron Saint of Domestic Appliances: due out in February. Credits will be in the shownotes. Many, many thanks. Dave Burnham http://www.adastralpodcast.com