LOL!...funny you mention "frozen". A couple of years ago when riding with the Northern Colorado Trail Riders club out in the San Rafael Swell, one of their club officers kept accusing me of having some "dry iced" ice cream in that rack bag and threatened to break in to it at each rest stop on the trail.

Actually it has some tools, parts, and such that wouldn't fare as well if soaked with water, so all my WalMart plastic sacks go to good use there.