Jumbo... sorry if I missed part of your description... back in the day, when guide rods were of sufficient diameter, and the recoil plug was inserted from the rear of the slide (we initially had to remove the rear ledge of the slide), you could lock the slide back, mark a spot on the bottom of the guide rod just in front of where it exits the slide... then drill a small hole large enough for a paper clip diameter "L" shaped bent wire, making sure it clears the dust cover
to use: you would lock the slide back, insert the wire, then slowly release the slide which would trap the plug to the spring and guide rod so it could be removed in one unit... to install, you slide the unit in, hold upright, and lock the slide back.... the wire would fall out