Don't worry, this TB/coin is probably NOT missing at all.
But visitors in Amsterdam often wait until they get home before they log their founds. And that can sometimes take a long time! All the while the TB is listed on the cache-page, which disappoints other cachers (they find an empty cache).
Hence, I mark it missing. When the user that has it logs it, all will be restored.
Kind regards,
DopamineNL