If you do forget, and the bag of trash remains in the trunk for the duration of your work day, your car will smell like something curled up and died in your front seat. Yes, I did this just this week. I would love to say that this is the first time I have let this happen, but it's not, and it most likely won't be the last time.
Luckily, the smell is now out of my car. If this saves even one car from smelling like roadkill, then I guess it was all worth it.