right after Baby and Jonny quit practicing (before the log scene) he kicks out the pole and then smashes it through the window. The window then shatters in to many tiny pieces. At next shot, we see the same window with one small hole in it.
If you notice when Johnny lets Baby into the car and he's running around to the other side You can see baby unlock his door but you have to look closely.
I believe that it is the other way around, when he smashes it, the window doesn't shatter, there's just a small hole that Johnny sticks his hand in. The slip up is when they are driving away. In the next shot the whole window is gone.
It looks like right before they cut to him unlocking her door, the window was smashed to pieces, but they cut out of that second shot of him hitting the window for you to really tell how much of the window was smashed. I believe the real slip-up is the next scene where she says, "You're wild!" The hole in the window is much larger than the scene before.
Amanda, OK. first of all, of course she unlocks his door! was she going to sit there and let him break another window to get in? Wouldn't you unlock the door even if he had the keys?? I know I would regardless!