I failed to mention one thing, the screw just under the front of the trigger guard is missing. It appears that it lines up with the pivot of the release lever. Are they related?
I got the left sideplate off (2 screws, one long through to the opposite sideplate and one short into the receiver) and it's not that pin. I've yet to be able to get the right sideplate screw (one screw) out. My 12 only has the one through bolt.