Same problem here with my site buzzfrance.fr.

It's been de-indexed from Bing for a year now. It's a high-quality website with a lot of traffic (now coming almost exclusively from Google) and some of my users are complaining that they can't find it on Bing.

I have been contacting the wemaster support about this for a year and I have no answer. It's really outrageous that they remove so many legitimate sites from the index automatically without any reason. I know other people to whom it happened, same story.