I don't think it's as big a deal as some of the others.
If his pilot certificate has never been revoked or voluntarily surrendered, it's still good. The certificate status is pretty easily verifiable through the FAA database. The idea to have him get a copy of his FAA records is a good one - at least provides a baseline of some numbers and verified the existence of the certificate.
Certificate itself gone? Order a new one. In fact, do it anyway, especially if his old one used his social security number. Order up a new one and update the address information and you've killed a couple of birds with one stone.
Lost or threw out his old logbook? No big deal. He hasn't flown in a long time so currency isn't an issue. Neither are qualification for certificates or ratings - he already has them. The only real issue with the lack of a logbook is that endorsements (or evidence of flight time before the applicable dates) for things such as HP or complex aircraft would be missing and, at this point, probably irretrievable. So you do them again if he wants to - with a lot of time away from flying, it wouldn't be a bad idea to get the complex and HP instruction over anyway.
When coming back to aviation, relearning old skills and knowledge, learning new skills and knowledge, and blowing rust off are the big deals. Whether he still has some pieces of paper recording flight time that doesn't really matter that much is a non-problem.
I'd handle his FR/PC the way I'd handle it for any other pilot who'd been away from it for a while.