I don't know why a huge drug store chain like CVS can't keep their shelves properly stocked. Especially in the case of sell items. When an item is on special you would think they would keep it properly stocked to ensure customers can get in on the deal at hand. I know that some stores that deal in over stock items are a first come first serve on their deals. Such a store is of course Big Lots, they can have advertised specials but its always while supplies of the items last. For example my brothers went there to get in on a great lap top deal, but they only had one left that was boxed up. They offered to sell one of my brothers the display unit at a more discounted price.
My husband worked in a retail store and such cases happen because of several reasons. First they usually are only clearing their shelves in preparation for new stock so there won't be a lot of items left. Another reason could be because they want to drum up interest for their products so they'll put limited items on sale and hope that their other products that are at regular price will catch your eye.
I have had the same problem here for me its walmart it seems like they don't even stock their shelves anymore period it's really annoying.
My local CVS stopped giving rain checks. I don't know if the entire chain has stopped rain checks, but my local stores don't do them anymore. So now if I want any hope of getting those sale items before they sell out, I have to go the same day that the sale starts.
I have noticed this is happening more often and not just on sale items but on some generic brand items as well. I usually just get the generic brand vegetable oil but there wasn't any stocked on the shelf except for the gallon size! This would have forced me to purchase a name brand for the size I wanted. I ended up buying a much smaller size name brand instead. I have had this happen a lot lately to a lot of other products as well. I am beginning to think it is a way for the stores to move name brand products.