I forgot to address your specific situation. The editors at the magazines in question are very busy guys. Remember my comment about Email? They probably have a few dozen Emails (at least) waiting for them every morning, plus regular mail, phone messages, incoming photo/article submissions, etc. Not to mention an entire staff to direct and another magazine to ship to the printer in four weeks or less. An editor would love to be able to honor, immediately, any request for material to be returned, but they rarely have time for it. It takes time just for them to delegate the task to someone else. You need to look at their masthead, see who's listed as editorial secretary or editorial assistant, and contact them. They'll still need to run the request by the editor, to make sure the material isn't something they plan to use, but the process will stand a much better chance of getting started and carried through.