I searched for "cowboy santa" and two tissue papers appeared - each in stock and not showing as discontinued when you click through from your store front.
I believe the problem is with your collections and the fact that when you created those collections and added the 20 x 30 18lb tissue paper to them - that size and weight (now discontinued) has stuck within the collections.
You could create new collections with the new sizes/weight or remove the discontinued sizes from your collections then re-add them with the new sizes
Otherwise, without this housekeeping when a customer clicks through a collection to the product page they will come to the Heads-up page
Tell your customers to change from the 18lb Tissue to the 10lb which shows in stock and then choose which size they require
You've already contacted Zazzle directly about the issue - and nothing seems to have been done to correct the sizes within the collections that you have.
It's now down to you to make sure your collections have tissue papers that lead to an "in stock" product page.
@Rena Yes you can quickly and easily create a new collection using Bulk Actions in the back end of your store
Drill down to the tissue department in the left hand panel
On the right - select Bulk Actions - Select all non discontinued products
In the Bulk Actions - Actions - select "add to collection"
then add to new collection at the bottom of the pop out window
Then fill in all the collection details as you normally would and wait for the collection to index
