Sorry this happened - If you weren't from Jersey, I'd say someone probaby cut it, but after the weather we have been having, it actually might have happened from the wind or when something small hit the plastic. Early one morning, I went to take out the plastic cover for my son's stroller (similiar material) and it shattered in my hand when I went to pick it up (didn't use much force) and the normally flexible material was as brittle as paperthin ice. one piece I brought inside was fine once it warmed up. Not sure how cold it was out, but this was INSIDE the car...
I KNOW there are other places that get MUCH MUCH lowere temps, but I'm just tellin' ya what happened when I came across a similiar material at sub-frozen temps...
Hope you are able to get it repaired for a decent price - till then, seal it on both sides with clear packing tape and call it a day.
[This message has been edited by FieroRumor (edited 02-03-2011).]