I've been to Boulder many times (my brother lives there), and it seems every third vehicle on the road there is a Subaru of one kind or another. This seems like the kind of mishap that has probably happened before, unless it was a totally random freak occurance.

My 1up rack doesn't even use a through bolt, just a wedge ball to keep it secure. On the one hand, I can make it extremely tight if I so choose. But it is events like the OP's that worry me, in case that thing ever decides to wiggle its way loose.