i encountered this also. so far i tried to manually resubmit links for indexing, and also resubmit the sitemap. my sites are not spammy, but they are not completely legal either, in some countries..
i think bing has some kind of team that works to delist sites that are spammy and/or illegal. they have an alert system that catches sites that start instantly getting traffic, possibly because they are in this field where lots of more prominent sites have been delisted, so search algorithm kinda attacks these new sites, starts showing them on SERPS, which triggers a signal and site goes thru machine and possibly manual validation, certain keywords probably set off alarms and maybe manually they finally decide to delist.
google delists websites too, especially last couple of years, but there needs to be a report, which you cannot reply to, but still you know who asked and what pages got thrown out. BUT if you simply 301 delisted pages to new different URLs, they eventually (1-5 days) get back into google. the more this happens, the less is the respect from google to your site, eventually it may be indexed, but won't show up on any searches, except "site:domain.com".. in any case, because i don't want google to see any redirects it doesn't need to know about, i have specifically concocted a detect mechanism for bing on some of my sites that are delisted in bing, did new URLs (for my sites have 1-20 pages, easy with php), and new sitemaps specially for Bing, this happened 1 weeks ago, actually did it for quite a few websites, and so far 1 has returned to bing, got reindexed, but honestly i am not sure if it was my doing, because indexed URL is old, not the new one i made specially for bing.. well, now i wait and see..
a quick solution would be to simply make a new domain with same website/content, and bing will gobble it up, but it may last a few days, may last a month, eventually they will delist it simply because it already set off their algorithms - it will happen again..