Every once in a while when a sale item is unavailable they will replace it with something else.
For example today at Shoprite there were no more Charmin 12 pks so they were replaced with Quilted Northern 12 pack, The Charmin was on sale this week for $5.99 but there was a “Super Coupon” in the ad for $2 off making the 12 pk only $3.99. So instead you got the Quilted Northern for $3.99. I had a coupon for Charmin for $1/1. Since the store replaced the Charmin with Quilted Northern when I presented the Charmin coupon they still accepted it. I have had this happen a few times and managers are usually very quick to manually enter the coupon for you.
So if you ever find that a sale item has been replaced don’t get discouraged and not buy the item, you CAN (of course this is depending on the store and the particular manager) but most of the time at least, you CAN use your coupon on their “substituted” product. 🙂