You should be able to shake it out through the area where the wiper connection rods fit at the bottom of the frame. Put that piece back (using a large screw driver or one of those tools with a magnet on the end). When you see at least one of the threaded holes, put a bolt in place to hold it from falling back inside. Move it to get the other hole aligned and put a bolt loosely into place, then squeeze some RTV into the hole to go between the windshield frame and the threaded plate. Now pull the bolts snug and let the RTV set & when that's done, you're ready to re-assembly everything.
You'll probably need to remove the wiper connection rods and maybe even the shafts that go through the windshield. The rods pop off - the joint is a steel ball and plastic (I think it's nylon) cup and I use a trim removal tool to pop the cup off the ball. When reassembling, you'll need to take care not to bend things - I use a pair of channel-lock pliers to pull the two pieces together. If you need to remove the shafts, they each have a nut on the outside of the windshield. Once that's removed, the shaft & associated bushing will drop through - you might need to tap it out. I use some windshield caulking when I put these back into place to stop any leaks.