Missing Participants

[BTG]

Has anyone seen any guidance on how to handle missing participants in an ongoing defined benefit plan? I'm having a surprisingly difficult time finding any. There seems to be a lot out there on DCs and terminating DBs, but nothing specifically applicable to ongoing DBs.

I would think the search methods for DC plans set forth in FAB 2004-2. However, if the participant is not found, the distribution options aren't feasible in the DB context. What should be done when missing participants start hitting their required beginning dates?

Thanks!