I did the same thing, I was showing off with the 5.5 brushless cranked up to full power, screaming around the car park at work on some old knackered tyres, and I got a turn wrong and clipped a van wheel at about 30 miles/hour.
It did exactly what you describe, the front of the arm broke off but the rear stayed in one piece and bent the hinge pin. Ah well. I'll have a ruhmmage through my spares box and see if anything else fits. I have a feeling they'll be the same size as outer hinge pins off a HPI Hellfire, in which case I might get the titanium nitride ones that HPI do...
-Steve