Cam shaft sproket bolt and dowel pin broke

[joeclarktoyota]

I bought a 96 Protege (1.5L) from a lady who's mechanic said it had a broken timing belt. I started taking it apart and found the belt was OK but the bolt that hold the plastic cam shaft gear on and the dowel pin are broken. Took valve cover off and turned cam with a wrench, doesn't seem to be frozen, also motor turns over OK. What would cause bolt and dowel pin to break.??? stuck value or ? Hard to diagnose when I didn't hear it run. She said she was going at a slow speed in her neighborhood when it quit on her. Where should I look? take hear off? or put new bolt and dowel pin in and start it up and see what happens??

Update - put everything back together, engine started and runs very smooth, no sign of any problems. The gear is metal, not plastic.....still curious what caused it.