it is an odd question but do Plan Administrators have any discretion to require that distribution request documents are notarized by the participant. in this case they are suspicious that maybe the participant is not at the address and they when they call someone else answers the phone.

Plan administrators have a duty to deliver benefits in accordance with the plan terms. If the plan says that the participant is the person who requests a distribution, the plan adminstrator has the duty to make sure it is not someone else and has the inherent power to carry out its duty, subject to express terms of the plan. In extreme cases, the plan administrator must disregard plan terms if plan terms are inconsistent with ERISA. The plan administrator can take extraordinary protective action based on reasonable belief.

We ran into a similar situation and were advised by legal counsel to do exactly that...ask for a notarized signature. We knew going in that the participant was not at the address so we simply wrote it in the distribution letter requesting that the letter be notarized. Took a few months, but the participant's family got the notarized signature and everyone was happy.

There are notaries who will notarize anything for $20. I tell them to send photo copy of license and SS card or any thing that has SSN and DOB.

That doesn't ensure anything either. They could very well have that information available depending on their relationship with the participant. I still say go the notary route. At least then you're limiting exposure as a reasonable person would expect the notary to be legitimate.