My bet is that it'll happen again.
The heavy guide rod likely broke loose due to its greater inertia, compared to the plastic it replaces.
Objects at rest tend to remain at rest, according to Newton. The gun moves back and upwards in recoil, but the massive guide rod wants to stay where it is. The gun moved, the rod didn't, and the two parted company.
I understand the desire to control recoil by adding weight, but a much better method is to learn to hold tighter and take the shock with both entire arms.
Your arms won't fall off, but eventually the replacement guide rod will.