Remove the button bank under the stereo and remove the Torx screw hidden underneath.
Pull the surround off of the car. Open the glove box if you have one, grip the surround at
the top and pull both sides off. It's a touch heavy handed and you will have to bend it a bit
but this is better than removing the entire dashboard to get the surround off.
Remove the 2x Torx25 screws from either side of the drawer.
It will now slide out of the dash when you pull it.
You can now retrieve whatever it is that you lost.
How to fit a double DIN stereo.