How to Fake break in to someone's car for a prank

If you have a friend who always leaves their valuable possession out in their car, where anyone can see them and only need break into the car to take them, you owe this prank to them to teach them a lesson. Get some broken glass and a key to their car, wait until they're out of the car and have left their stuff there, then take the stuff, roll their window down, and leave the glass around the window. When they return, they'll think someone broke into their car and robbed it. Really, it was you, the great friend that you are.