I believe that every UU worship and conference is, or should be, a soul retrieval ceremony.
Here's a list of some elements that help bring hidden souls home:
* Safety. The first requirement for a successful soul retrieval is the establishment of a genuine community space where the person will be welcome for who they are.
Note: Filling the room with "love" and "white light" can tend to keep the authentic self away. The goal is not "goodness" but realness, and acceptance.
* Beauty, pleasure, fun. Make the world an attractive place to come to.
* Naming, history, orientation, storytelling. The missing soul is lost, alone, confused, and afraid. Tell it stories that name its experience, factually or metaphorically. Reassure it, and offer it a path to come back into presence and community. (This can be as complex as a long series of rituals or sermons, or as simple as the usual conference orientation speech, or a good game of All My Friends and Neighbors.)
* Meaning, purpose, mandate. Give the soul a reason to show up. Explain why it is needed, why its energy will be welcome. If you come back, you can help your friends. You can change the world. Your energy is needed, your wisdom, your power, your capacity for deep feeling. I know you had a good reason to leave, but listen, there is a reason for you to come back, and stay.
(Note: for a more individual therapy-style discussion of soul retrieval, see the book by that title by Sandra Ingerman.)