There are no warranties for QVC jewelry unless a third party vendor offers it, similar to Eternagold or Effy on ShopHQ.
If you buy a ring with a lot of small diamonds, it is likely that the prongs are very small and delicate. They only have to catch once on a clothing thread to bend open and endanger the diamond security.
The same issue can happen with any precious stones set in prongs, which is why jewelers always tell people to get their engagement ring prongs regularly checked.
Please note that is not necessarily a manufacturing defect!
Many of the Affinity items are lower in gold weight, which means the prongs are not very strong.
There are jewelers who can replace lost small diamonds for a reasonable price, or who can hammer down the prongs to be more secure, if they are not real, real tiny.
Fine jewelry is not indestructible. Care should always be taken when wearing gold and diamonds.