Okay, so I have this nebulous anecdote in my memory, which I recall coming from a reliable source at the time, but I don't remember where--and I've been trying desperately to find the historical details and am coming up with absolutely nothing.

The premise was that the editor of a heavy mathematics journal, or a science magazine/newsletter of some kind, immediately knew about the Manhattan Project when it started--or perhaps a different Secret Thing, but I do think it was the Manhattan Project--because he noticed an abnormal number of his subscribers changing their mailing address to Los Alamos within a few weeks of each other.

I've googled every combination of words I can think of to locate the origins of, or any reference to, this story. I will throw myself prostrate at the feet of anyone who can help.