Briney will take us to Orre to snatch it from Micheal at the last moment.So this is sorta off-point but will lucky egg be a gift item in the game? It's been available since b/w and it's near impossible to find it on chansey(i'd know, i always obtained one in platinum taking 3-5hrs.)
Is lucky egg still relevant to your playthroughs? Would it make any difference if it wasn't included in oras?
I never really made much use of the Lucky Egg myself, outside of completing my dex in Diamond, even after it became standard to get one for free. But I don't see it making anymore of a plot difference for the Lucky Egg to show up at some point than it would to replace the Exp. Share with the Exp. All, which I would not be surprised to see, given the fact that for them to revert it, it would have to become a hold item again, and thereby open it up to be sent back into Kalos.