Anyone ever hear of this happening before?

I have a set of '01 Avid Mech. on my GT, and was riding yesterday. I was going down a very rocky but fast decent, hitting my brakes fairly firmly and my rear wheel seized up. At first I though I got a stick through my spokes, but then tried to spin my wheel and the rear rotor was totally bent. I mean it was an inch or two out of true. I don't know if a rock hit it or if some how it heated up too much because of the friction? I had to take the calipers off and duct tape them to my frame up by my seat and then bend the rotor back with the heal of my foot so it would pass through my frame without rubbing the seat stay. So I made it down the mt. with only my front brake. I found a new rotor on ebay for $10, luckily. I thought the whole thing was weird. So anyone ever have a rotor do that before?