Hi David, I'm so sorry to hear that happened. I think it might have broken because you didn't use the bead buddy quite right. When you spoon the tire back on properly, there is hardly any strain on the plastic bolt. The plastic bolt is there to keep it loosely in place, so it doesn't damage the rim. That's why competitors like Motion Pro also use bead buddies with plastic screws too, to keep the rim safe.
I've sold probably over a thousand, and I haven't heard anyone else report the same problem. You do not need a steel bolt.