The last time all I wanted was to check out the riverfront beach as a possible float trip take-out spot, and there were well-beaten trails identical in size, with no signs, where there was no indication of forks in the trail on the map. Grrr!
They probably weren't official trails. Just paths left by many people hacking it on their own in the same footsteps. The park doesn't want you doing that and destroying possibly delicate land, so they're not going to condone the activity by promoting it to an official trail on their maps.