It's going to end up behind the dashboard.
No point in removing it (unless it was something you needed).
In order to get it out you'd have to start stripping the dash down. By the time you get to it you'll probably have created more rattles and squeaks because of broken plastic clips. You can look underneath the foot well to see if it fell all the way through, otherwise just let it go.
2013 335i M Sport /// Alpine White/Coral Red