So I shoveled all the snow back around their car, and left a sign. It said:
Hi. I spent a lot of time and energy shoveling back in your car, and searching for your video surveillance. Unfortunately, I was unable to locate your video camera, and was therefore unable to remove it. However, I assume I will see you undigging your car, and will use that opportunity to stand and watch and laugh so hard as to be worth your slashing my tires. To ensure I have sufficient time to see you undigging and enjoy, please note I have poured water over the snow pile. This is not a promise.
You think you were laughing hard? I put up the sign, but some other poor shmoe was the one who parked there!