One of the more poorly-worded (or brilliantly worded) pieces of regulation I've seen.

I kind of wonder what would have transpired if the OP had provided his pilot's certificate. What then?

If it was expired, I'm sure that would have been pointed out. So? I have kept old IDs for a variety of reasons - nothing illegal about it. Would the agent have black-lighted it? What fields would have been checked? Would a copy have been taken (almost certainly 'yes')? If the agent saw something he didn't like on the certificate, would he have used it as grounds to confiscate it or to prevent the OP from entering the sterile area?