The server currently uses LogBlock at the moment, and i’m not too experienced with that plugin. I know for a fact that it (the scenario you described) would be entirely traceable with quite a few of the major open-source logging plugins such as CoreProtect. It may be possible that the current plugin just lacks the functionality to do so, but then why use it when better alternatives exist?
Perhaps changes will come with the server upgrade? Til it’s safe to trade gift cards, I’ll only accept them direct to my email. If I was to use them straight away, it wouldn’t be such an issue but I hold onto them for quite a while some times.
Recoding gift cards should be added to the shop because it's a legal item to trade on skyblock and it's also very risky trading them because who knows how many people have access to the the same code. The trust system is hard to believe in when "real money" is involved.