Welche Bedeutung steckt hinter der hier vorgestellten Vokabel aus dem Bereich Colleague to colleague?

Kathie: 'Whatever happened to the rule that said we couldn't wear jeans at work?' Ron: 'Oh that! It sank without trace.'

to sink without trace

Do you know what it means?

• to be intended as a joke
• to disappear completely and no one knows where
• be cancelled without notice