What could have happened is that the center bolt that holes the diaphragm to the arm assembly came loose. This will cause an impact effect, breaking the washers. There is suppose to be a little Loctite on the bolt to prevent it from coming loose. You're very lucky no pieces fell into the timing chain.

Depending on how much is damaged, there is a diaphragm repair kit, valve repair kit, and rocker arm repair kit. Not sure if the diaphragm or rocker kits come with those washers. Anything other than that and you are looking at a used or new pump.