Out of Stock items can specifically be checked by selecting the Out of Stock filter in the top left corner as shown below.

Once you have this list selected, pick the item you are looking for in Date Check Pro and find it on the store shelf.  Once you have done that, you should check every product on the shelf to make sure that you can enter the next closest date to today.  Upon touching the item on the screen, it will pop up with the screen below to allow you to enter that information.  

If the item is still out of stock or has been discontinued from the store, you can also select those buttons on the left and right side of the number pad, respectively.