So, that's the question: What do the four hex head bolts that hold the Honda 45L top case mounting plate on screw into?

I can't find any nuts underneath them that they screw into. Do they screw into some sort of threaded sleeve molded into the plastic/body somewhere?
The right front one on mine just spins and isn't holding that corner down anymore. Help!

I can't find any nuts underneath them that they screw into. Do they screw into some sort of threaded sleeve molded into the plastic/body somewhere?
The right front one on mine just spins and isn't holding that corner down anymore. Help!