Although I don't have a picture of it, I believe that "Keiser tee" for #1 is just below the deck/patio to the left of where you come back through the plexiglass opening after finishing #18...Maybe it's just to the right of that pathway, I can't remember..
Anyway, if you turn around while standing on the green tee and look back to the back left of the 18th green, you can see a flattened spot that is partially overgrown, and that is where I have been told that tee is/was...
There also appeared, in the early days (1999/2000), to be a flattened probable old "Keiser" tee off the right side of the fairway of #17 at Bandon Dunes, as Ryan has said. I believe it made that hole a long par 3 carry all the way over the canyon, but I may not have that quite right. I bet that one is not maintained any more, either...
We all post on this topic every few months, about the hidden tees, just this time I made a point of actually photographing one...