I got a result, but only by emailing bwtsupport at microsoft dot com. They resolved it. I also sent a letter to their legal dept, but I think emailing their support did the trick. This is not a published email I dug it up in a forum post. Worked. Hope you get help too.
A Microsoft forum poster suggests an alternative email address, bwtsupport at microsoft dot com, for raising concerns about Bing de-indexing. This email is listed in some older posts from the official Bing blog. I have not personally tested it yet but will keep a note here.