I have a copy FASB 2004-02 which deals with finding (or, trying to find) lost participants in a terminated plan. Is there anything out there on finding lost participants in an existing plan? I'm thinking much of the methodology would be the same.

I would think so.

Search these Message Boards (that is always good advice) for links to the IRS and SSA letter forwarding programs.

IRS Notice 94-22 Here

Here are the IRS SItes:

http://www.irs.gov/retirement/article/0,,id=110139,00.html
http://www.irs.gov/retirement/article/0,,id=110142,00.html
http://www.irs.gov/retirement/article/0,,id=110108,00.html

SSA SITE http://www.socialsecurity.gov/foia/html/ltrfwding.htm

I understand about the letter forwarding programs.

FAB 2004-02 describes other methods (such as contacting beneficiaries and using the internet), and what to do with the money if these people are not found.

But it addresses terminating plans, not existing ones. I was wondering if there was a similar document for existing plans.

Here is FAB 2004-02: http://www.dol.gov/ebsa/regs/fab_2004-2.html

Do you need another document for existing plans? Don't the principles apply to any search for missing participants?

Why do you want to devote time and $ to finding people that dont want to be found and didnt provide a forwarding address. Not everyone who is located by the IRS or SS will claim their benefits. The plan can adopt a provision that forfeits benefits of missing participants when they are available for distribution (to prevent violating the MRD requirement) subject to reinstatement if the participant reappears to claim the benefits.