The bonnet was raised yes, the rubbers exert the tiniest amount of preasure just to stop it from rattling. You can close the pins without pushing it down.
I would put money on this being the cause - either by air pressure pushing up on the bonnet at speed and either snapping the pins or forcing the bonnet sideways (a direction it can't normally go in due to the wing gutter it sits in).
Or more likely the front catch either not latching properly or being under stress as the pin will be sat in the catch at the wrong angle due to the bonnet not being down properly at the back. The catch was not designed to hold a bonnet that is not fitted properly.
Apart form that, all motorsport products are sold without any real guarantee due to their intended useage unless it is obviousl manufacturing faults.
Any pictures of how the pin actually 'failed'? What broke, or did it just come open?