untraceable

The thief left an untraceable trail behind him.

She received an untraceable message from an unknown sender.

The hacker covered their tracks well, making their activities untraceable.

The spy used untraceable communication methods to avoid detection.

The company received an untraceable donation from a mysterious benefactor.

The criminal used untraceable currency to launder money.

The virus was designed to leave an untraceable mark on the system.

The whistleblower provided an untraceable tip to the authorities.

The anonymous tipster left an untraceable note at the police station.

The transaction was made using untraceable cryptocurrency for anonymity.