I'm not sure if you can do it on behalf of a website, but Bing Webmaster Support has been pretty responsive in my experience with my own domains, like an actual

I'm not sure if you can do it on behalf of a website, but Bing Webmaster Support has been pretty responsive in my experience with my own domains, like an actual person emailed me back after a couple days. And since Bing seems to feed a lot of DDG's index, if it gets back in Bing it will probably also go back to normal in DDG.