Your points may have been exchanged to a promo code that was generated when you hit 'redeem' on your points at the cart or check out page.
The points won't actually show up again on your point balance but if you have not used it yet, it is still valid. You just need to use the same code again when you want to place your order.
The code will be saved in your Rewards History page so you can copy and paste it directly from there and enter it in the promo code box at checkout on your next order.