I know that we all feel terrible whenever one of our badges is up for auction on Ebay, but this is truly outrageous! That badge is a living piece of history for your Fraternity!!! I would be foaming at the mouth if I found one of my Founder's badges on Ebay.
I'm glad one of your brothers won the auction. I hope that it eventually goes back to your Headquarters, where it should held in posterity for ALL the brothers to see.