This week's local newspaper identified two bodies found in October on local beaches, one at San Gregorio (where the bone fragment in which we are interested was found) and one at Miramar. Both people were identified as suicides who had jumped off the Golden Gate Bridge, which is at least 30 miles north of Miramar and probably 40 miles north of San Gregorio. They were found last month. This is of interest to us only because it shows how the prevailing currents work, and how very far a body (in these cases, adults) could be moved before washing up on a beach.
This information, plus the letter in Searching for Anna from Dr. Dave Mustart, chairman of the Geology Department of San Francisco State University, makes it rather unlikely that the bone fragment could belong to Anna. On the other hand, there doesn't seem to be an unidentified who would fit the age window. What a mystery. I wish they would get on with that DNA analysis.