Email Mentor. Tell Mentor that Friend will be moving to Undergradville. Attach Friend's CV.
A few days later, Friend emails Mentor, also with Friend's CV attached, mentions your name, and inquires if Mentor's department has an adjunct pool, and if s/he might be placed into it.
Yes. I've received such e-mails ("my friend so and so is moving to Your City, and works in our field") with c.v. attached. If it looks good, I pass the c.v. along to the person in the department who hires adjuncts in that area; if it looks really really good (and comes from one of my former PhD's who I see often at conferences and so forth) I may also send a quick "PhD. has mentioned that you're moving here; get in touch when you're settled so I can let you know about the local monthly inter-college forum in our field and other things that might interest you.")