When I just checked, it no longer shows local availability for the S&B primers, which is very odd, it was working earlier today. I can still see local availability for CCI, Winchester, and Federal primers, but they are not on sale. Maybe the sale price is for online purchases only and they have updated their web site to reflect that?
But, the function for checking availability is located on the product detail page, at the top of the table which lists the products. There should be a pull-down to select the state and store, and the availability will show up under the "Add To Cart" button in the table. Hope this helps!
Edit: the pull-down is not available for the S&P primers, you'll need to try a different product, such as the CCI or Federal primers, gun powder, etc.