I believe there is a limit on the number of items a merchant can have for sale, unless they make a certain amount of sales. IIRC, it's three. Unless you're a bestselling merchant, in which case you can have as many as you want.

I think any item that doesn't sell well is pulled. First it's moved to the warehouse, and if it still doesn't sell, it's removed. So it may not be the merchant who pulled the product.

You could try looking for the item in the other stores. And some merchants have sold their products to third parties. DarkWhispers' V1/2 stuff was sold to DAZ, I believe; they are slowly releasing some of it, mostly in the PC.

But yeah, V1/2 and M1/2 products just don't sell very well any more. Not that many people are still making them, so as the older products are rotated out, there's going to be less and less V2 stuff available. Buy 'em now, while you can, I guess.