"There was considerable sand on the greens because there appeared to be no discernable lips on the bunkers. How serious of a mistake is this?"
Mayday:
Serious!!
And very likely a serious mistake even from some of golf architecture's greatest architects of the great "Golden Age".
Have you ever wondered why those incredibily beautiful ORIGINAL bunkers at CPC, and also the incredibly beautiful "Imitation dunes" at Pebble that were built at the same time didn't last?
Look at photos of those original bunkers---they are so low profile (really low lips) to greens particularly it almost looks as if the greens were pasted on.
One thing we know for sure is that Mother Nature certainly hasn't changed!