Hi mitymau,
You can place the Auctiva store window back in the listins from which it was deleted by first copying your store window HTML code after clicking the "Store Window HTML" link under the "Store" tab within your Auctiva account. Then, procede to eBay's "Revise your Item" form and paste the store window HTML into the HTML version of the editor wherever you would like it to appear, and save your changes.
-Mike