The Preparation H trick works as a one off to get a prolapse back in, but that us far as it goes with that. Prolapses can pop in and out, but if they keep happening, it is a serious health issue for the hen. It will also encourage pecking by the other hens
If you take pictures of the protrusion next time you see it, it would help a vet to diagnose the problem. If it is a prolapse that is repeatedly happening on egg laying, the vet will almost certainly recommend you put the hen to sleep.