That's the only F%rd part of the truck. lol
Tape your socket onto the extention because I know of no magnet that will
get something out of a place like that.
I haven't droped one in there before but I can imagen hearing it roll around in there while driving.
Trucks with no dome light have a metal plug you'll pop out with a screwdriver.
Trucks with a dome light have a rubber plug with a wire going through it that you can pull out with your fingers.