I have over 900 reputation and over a year of answering others programming questions on Stack Overflow, and I had a Unsung Hero gold badge about 2 weeks ago and I had just gotten it and within like a week it was gone and I got like 60 notifications of all of my badges being given to me (as if they were all taken away and given again) but the gold badge (maybe along with others) was not re-given. Can you lose a badge you earned? God bless!
Note: here is the page (just found it in my web history) of the badge I earned: http://stackoverflow.com/badges/226/unsung-hero?userid=773897
I may no longer meet the requirements for it, I don't know, but should that make a badge disappear, I feel like once you've earned something it should be yours to keep... just because I start answering more questions with different +1's or whatever makes me lose my only gold badge? In that case I should have just stopped answering questions hahahaha! :D
Here is a screenshot from my browser's (Safari's) history feature that shows me having 1 gold badge: