So Friday afternoon my dad's truck broke down, we thought it was the starter, but when we took it to advanced auto's they said it should be fine, but one peice broke off so we had to get a new one anyway, however, when I went under the carriage to put in the new starter, i saw a bit of wire, that looked sheared off, it's part of the main wiring line that goes to the starter, i included pictures, was it a sensor? or something else that broke off that we have to replace? please help.

 

That looks like it could be the battery feed to the starter. Have you tested it for power? In any case this should be cleaned with baking soda and warm water. It most likely had an eyelet on the end.