I've had that happen once with an NOS tube, Jim. You can glue it back on with some two part JB Weld and it should be as good as new. Obviously take care to put it back exactly as it was so the key orients the pins properly. It certainly makes getting the orientation easier, but does not have to be there to do so if you are careful. You could try using a pointy L-shaped dental tool to get some purchase on the interior of the piece and pull it up slightly. I think you can find similar tools at a hardware store or hobby shop (don't use these for your home dental practice though). Once it breaches the edge of the socket you can grab it with a pair of needle nose pliers. You could also search out some kind of expanding bolt fastener for attaching things to drywall. There's probably one that would do the trick, though I'm not positive. Insert the expanding end and hold it with a pair of pliers while you screw the bolt down to expand it. Once expanded pull the bolt upwards. It may be a tricky thing to get out once expanded, but I bet a bit of twisting ought to do it.
Good luck.
Good luck.