2007 Diesel Injection Pump Failure

I have approximately 120,000 miles on my 2007 sprinter. Today i was stranded because the engine light came on and stalled. After a quick inspection along side the road, it looks like a small cap came out of my injection pump. Its something that looks like a . . . freeze plug for lack of better word. Could something other than a premature failure be the cause. I did hear some loud clunk just before it stalled out. I think that plug/cap hit the fan and shattered and this was the noise i was hearing.

Any help or ideas would be great. Right now I am waiting for my flatbed tow truck to take me home so i can work on it tomorrow and order parts.

Thanks,

Jeremy