Studiodog,
You probably have not lost the plate, it just probably just slid out from under the retainer and is floating around inside the hood edges somewhere. It is impossible to remove or replace the plate with the hood skin on! I have had to fish several of these plates back into position, and it is a tedious job! Once you locate the plate, shake the hood to get it into position where you can insert a magnet through the holes in the hood and grab it. You can then slip it back into position inside the little "U" shaped strap that holds it in place. Once you get it in place, insert a bolt that has the head cut off of it to keep it from falling out again. When you install the hood, get a bolt in the other hole before taking your home-made stud out. once you get the plate to where you can see it, it will become pertty easy to understand. The plate is "H" shaped and slips under the u shaped strap on the inside of the hood. The plate is not symetrical and can only fit one way and still have the bolt holes in the right place, so if you are like me, you will get it in upside down and then have to flip it over! The position of the strap is indicated by the two rivet heads that are visible on the hinge side of the hood.
Regards, John McGraw