This is a question I received in the comments on my site about finding the lost. I decided to answer it here as a Q&A post.
There are a number of stones used to find the lost or missing. Peridot is one that is highly thought of which can be used to find anything, including a person, that is lost Pyromorphite helps renew connections with people we have lost touch with, which can assist in reconnecting face to face. Other stones that are well thought of for finding the missing are Snakeskin Agate and Golden Topaz.
Another tack I might take is to use third eye chakra stones to enhance my inner vision, so that I might locate this person to see if they wish to come back. Some third eye chakra stones are amethyst, iolite, charoite.