This seems to be the case a lot more often today. Parts show on vendors web sites only to find out that there is no inventory or that the part has been discontinued.
I blasted a few people at Yearone a few weeks back.
They had the part listed(like some vendors) but they also showed inventory and a price. So I ordered it, then a day later, they tell me its no longer available... I think some vendors do this for click bait :-(
And that Classic industry ad you are referring to is also deceiving, I called Classic Industries last week about that ad, and they no longer have this item nor will they be able to get inventory as it's no longer manufactured.