On May 30, 2011, I earned the Mortarboard badge. You can see it on my profile using the WayBack Machine. (I also commented on it in a meta post the day after I earned the badge.)
I am wondering why this badge would be revoked, as I've read several times that badges are never revoked.
UPDATE 12/1: A little over a week after I posted this question on meta, a rep change occurred. Apparently, this question that I answered on May 30 was deleted:
This is confusing for several reasons. First, the rep change occurred over a week after this question was posted. Furthermore, that question had several upvoted answers, including an accepted one, as you can see from this cached version on Google. I was under the impression that questions with upvoted answers could not be deleted. According to Google, the page was cached Nov 24--two days after I asked this question--and you can see my rep is at 2,338. So this is not a case of an answer that was deleted long ago and never reflected in my rep history. This may be a coincidence, but if so the timing is very odd...
In addition, I had commented (below) that my /reputation page indicated I had gotten 200 rep on at least one day. Now this has changed. It says:
earned at least 200 reputation on 0 days
But the figures above are still accurate-- in my time line, it still shows 200 rep on May 30.