Today, I learned that Pokemon Bank can't store items.
I've just recently gotten back into Pokemon after being on hiatus since the beginning of Generation 6. I have a lot of mega stones I still want, and now I have to wait for my friend to be available to trade them back. I started playing halfway through Pokemon X, then lost interest in Pokemon (and Yu-Gi-Oh!, but that's another story) for a while. I purchased a copy of Omega Ruby about a month ago. It was used, and had a save file from the past owner on it. It was completed all the way except for the Elite 4, which I then beat, and I really liked the Pokemon on it. I decided I'd keep that save file for a while until I put all the Pokemon in Pokemon Bank.
Now, I have all of the Pokemon in Pokemon Bank. But the mega stones remain on both cartridges. I plan on resetting both cartridges and starting over again, but now I have to wait a while to get the mega stones. :/