By coming out freely it demonstrates that it broke due to tensile failure, not by bottoming or seizing in the thread. You should be able to tell rather easily with a file-test whether it was heat treated or not. Everything seems to point to it having bypassed the heat treatment process, thus causing the failure. A very small error, and at least it was an external part and thus easy to fix, but a major safety problem. I hope they are heat treating all of their blade plate retaining bolts by now. It isn't a failure mode you'd want to have happen to you more than once.
