I'm sorry to hear about the difficulties you are experiencing. If you only saved over this custom template on your Auctiva Custom Template management page, the active eBay listings you had already posted using the template should not have been impacted in any way. However, any new listings posted with the template thereafter would reflect the unintentional changes.
Since you mentioned this template is not showing up in your listings any longer, I suspect you must have actually deleted the template from your account. In that case, once you have added this template to your account again, you should be able to apply it to your saved listings it went missing from in bulk using the “Find and Replace” option on your Saved Listings page.
Once you have selected the items you would like to add the template to on your Saved Listings page, just click the “Find & Replace” button and choose “Listing Template” from the “Select Field to Update” drop down menu on the ensuing page and you will be presented with the option to apply a template to those saved listings in bulk.
If you also need to add this template back to any active eBay listings you posted from these saved listings, you should then be able to do so by revising each one via the following process (provided that eBay will still allow the descriptions of the items to be revised):
1) Click the "<HTML> icon to the right of the item on your "Saved Listings" page
2) Select All and copy the html in the popup window.
3) Locate the item on eBay and click the "Revise Item" button.
4) Scroll down to the "Description" section and then click the "HTML" tab above the description editor.
5) Delete the existing description HTML, paste the copied HTML in its place, and save your changes.
Unfortunately, we do not offer an option that would allow you to restore a template that has been deleted or overwritten so you may need to recreate this template from scratch. If you are able to locate an active eBay listing which still contains the template, you should be able to get the template code from the page source though.
I see that you ended up being able to file a support case about this issue after all, and I will make sure your case is updated shortly. If you need any further assistance with this, please feel free to follow up with us through that open support case and we will be happy to continue working with you.