I found my first one today...you can see it below amid the beans. These were all found on the pedestrian beach right in front of the visitor center.
You will also note a black bone fragment on the right side of the picture.
I haven't identified this one yet but it has some uniusual striations that should make it recognizable to someone familiar with such things.
I'm continuing to work as a volunteer at the center to help visitors learn about sea beans.