Long ago, in the dark days before disk brakes, I bought a used car and in a short matter of days, all the brake components came loose inside the right rear drum. I disconected the brake line, bent it over and mashed it flat with a hammer and drove it carefully back to the dealer. I had some kind of 30 day garantee and it was all fixed for no cost.
The mentioned bolt was most likely not tightened down and it worked its way out. It shouldn't happen but it did. Bring it to the attention of the used car dealer. You may even get your $45 back.
Glad your wife is OK. That's the main thing.
Enjoy your new Cruiser.