There is a secret AA Premium Services lounge at DFW. It is easy to find because it is located just a few doors down from the AC in Terminal A. Look for the PS logo (the eagle wings) and a sign saying "Private." On occasion, I've seen VIPs being escorted to and from the lounge to a Premium Service golf cart that conveniently is parked right outside.
I imagine (but cannot confirm) that such secret lounges exist at other hubs and major Premium Services stations as well, such as JFK, LAX, MIA, ORD, and LHR. Of course, these lounges would be invitation-only.
Basically, think about the airports that have heavy VIP traffic, and you are likely to find a secret lounge there where Premium Services can give dignitaries a little privacy before they walk onto their flights at the very last possible moment.