The lost has been found. vinyrd and I were on Nantucket this weekend. Vinyrd had found the cache before GC497ZH The Troll and Eel Skin Inn, so we knew what we were looking for. It had 1 previous DNF. So when vinyrd went under the bridge he confirmed the cache was missing but your TB was sitting on a bridge support.
The Girls Scout emblem is still attached, but corroded and the chain is rusted, so we will replace the chain and clean up the tag a little before we release it.