In Hollywood movies computer effects became a part of the business. Movies without computer effect cannot be imagined right now! Of course, using computer effects makes their job easier but addiction to computer effects sometimes causes funny mistakes.
Valentine’s Day movie there was not any computer effects and it does not need though. But we know that, car driving scenes are shoot either in front of blue screen or towed by a truck. In both cases, the car is not driven but it does not mean that actor should not act like driving. However, while we are watching the movie we should feel that everything is real! Because, we want to believe it like that :)
But they forgot something while shooting this movie, cars do not movie while gear is on P (Park position). This means car is stationary, not moving, parking and what so ever. You cannot move the car while the gear lever is engaged on Park position, it shoud be on D (Drive); it is impossible to move in P :) And here is it, a movie mistake!