I have been looking for that post for a while. I can't use the new BYC search feature worth a darn, unfortunately. I found several other posts that indicate this has happened several times over the last 4 years. The consensus was that using a sterile blade to cut a large enough opening in the membrane to release the egg was the way to go. No antibiotics were generally used after and the hens went on to lay for the remainder of their long lives. I am somewhat skeptical, but it was the same story each time and I found 3 posts relating to your issue.
Do your own research, but do it fast. This issue cannot be left indefinitely. The longer that prolapse stays out the greater the risk of infection.
Good luck.