IIRC, Vanilla Coke came back after going away for a while. Whether it’s gone again, I don’t know.
Sometimes they donate it. I belong to an organization that has a fundraiser every year; we sell raffle tickets, etc. We serve donated pizza and cake, and ask the local Coke and Pepsi distributors to donate soft drinks. They always have been generous, but one year one of them supplied us with their “novelty” flavors. I don’t remember which ones, but it wasn’t anything as mainstream as Vanilla Coke. Nasty stuff and we had cases of it left over. When they say “We couldn’t give it away,” they mean it!
There’s still Vanilla Coke on the shelves of most grocery stores around me (Dallas-Fort Worth area). I only ever see it in 12-packs of cans, though, at groceries. Usually gas station convenience stores sell singles of the 20 oz bottles.
I haven’t seen Vanilla Coke in awhile here in San Antonio. I remember one time when it had disappeared not long after its initial release, I stopped at a mom & pop gas’n’stuff store and saw Vanilla Coke 20oz bottles in the cooler. Woohoo! I thought. But it tasted awful, and a later inspection of the sell-by date explained why.