Missing pins are definitely a cause for concern. It is difficult for support to resolve the issue unless you have the pin urls, and of course, if they are gone, you don't know them. You did the right thing by contacting support.
If they are regular pins which link back to your website, some are still indexed on Google and you can find all your indexed pins by searching "https://www.yourwebsite.com" using the quotes. If you do this search and click on the listings of the Pinterest pins and if any have broken links, record them and send them back to support on Pinterest. I looked up your url and your Pinterest pins start on page 4 of the Google search.
To recover lost pins in the future, you may want to keep a file and record pin urls as you post them. That way you can report them and get a better response from Pinterest.
If you repost your successful pins, modify them so they appear as new pins. Change the titles slightly, the image name and even some pin content. This will give you original content and better response from Pinterest.
