That DID happen to me, last year. I was in Elko NV, photographed a very cool Norman Rockwell era church, then two months later saw the same photograph I made, from the same vantage point, but either framed or cropped a little tighter, in Lenswork. I wasn't livid but I thought my photograph was better and it made me wonder about how one gets published, etc.
And it seems to happen to me more and more often that I am set up somewhee, and just the fact that I have the 8x10 and the pack and the big wooden tripod draws tourists like flies. The buzz in, whip out the digiwhatsit of the point and shoot, and kind of blindly photograph in the same general direction my camera is pointed. Like they have no idea what's there, but if they just point where I am pointed some brilliance will appear on the their film or memory card.