The way it usually works is according to the trainers SID (secret ID). taintedshampoo RNGd the Bronzor, cloned the egg, then hatched one of the eggs on their cart.
I was then sent the egg (and the shiny version), and the egg, when hatched, appears to hatch shiny, and will be seen as a shiny sprite on the hatch screen, however, it was NOT really be shiny. When I go to my Pokemon party, it is actually non-shiny (because my SID is not the same as taintedshampoo's).
Unless by some miracle your SID is the same on both of your carts (it is possible, but HIGHLY unlikely), it will stay shiny.
You did look at your poke in your party AFTER it hatched, right?