This is sad.
This TB was dropped off by a finder in Taiwan at the official 2015 Geocaching Block Party in Washington back in August. Two months later the event still showed more than a hundred trackables in its inventory, including this one.
Suddenly, this TB has been marked missing by a Groundspeak lacky--without any kind of personal note to me--and now there are zero TBs listed at the Block Party event.
I can only surmise that dozens of TBs were grabbed by muggles and/or inexperienced cachers attending this huge event, and who thought they were some kind of souvenir so didn't bother to log them and keep them moving.
This was a customized geocoin given to me by my good friend and geocaching partner. Of course, I know TBs have an inherent risk of going missing, but this experience has soured my feelings about purchasing TBs in the future.
Lesson learned: I myself will NEVER leave a TB at a large event.