Is it possible for a rock to completely penetrate the clear bra?
Yes, anything is possible. This is, unfortunately, not a warrantable item. Clear bra/paint protection film is designed to be a sacrificial layer against the elements. Clear bra is not, unfortunately, completely impenetrable.
You might recall the video of the girl hitting our BMW i8 with her bicycle. This damage left a hole in the clear bra, but did not damage the painted surface. It is possible to potentially be so forceful, and so large, that it penetrates the clear bra AND damages the painted surface, but it’s fairly rare.
In this instance, think of clear bra/paint protection film like a bulletproof vest. If you get hit with gunfire while wearing a bulletproof vest, you still sustain a degree of injury (maybe pain, maybe bruising, but it’s also possible to completely penetrate).
The goal of clear bra is to drastically lessen the chances of any issues than if you didn’t have it installed at all.