A Bing Community thread has reports that when webmasters authenticate domains within Bing Webmaster Tools, the next day, the domains are no longer listed. Supposedly there are several reports about this in the past week or so.
Here is one report:
I (for the very first time) submitted several URL's, and I also authenticated my website by adding a LiveSearchSiteAuth.xml to my website sites, and I also submitted a sitemap.xml. They all showed yesterday.
But when I login today, I don't see any of my URL's from yesterday.
Brett Yount from Bing said that he is really not sure what is going on but he doesn't seem to be the only one reporting the issue. Brett said:
This is the third or fourth post I've seen today regarding this problem. I'm contacting our devs to find out more information.
This is not a confirmed report yet, but there seems to be something fishy going on here.
Forum discussion at Bing Community.