Hahahaha.
Okay, this is pretty funny honestly, I knew there was a reason I wanted to click this thread.
It could short the psu if it did land in it, I would imagine, but if it's on and functioning, I wouldnt worry too much. If you are really worried, turn your rig off, unplug primary power, unscrew psu from case, turn upsidedown, and shake *gently*