This week I experienced what others have reported... I walked past the marker for backcountry campsite 31 on Porters Creek Trail. It is hard to see... even in bright daylight.
The photo below shows the algae-covered marker and the campsite above the dry gulch in the background.
The marker is on the right of the trail about 30 to 40 yards beyond the landmark pictured below.
The log and two dead trees at the end of it are about 5 feet in diameter.
Be careful out there.