泥牛入海 (ní niú rù hǎi) | Meaning: lit. a clay ox enters the sea (idiom); fig. to disappear with no hope of returning | Chinese Idiom with Pinyin & Origin

lit. to throw a stone and see it sink without trace in the sea (idiom) · fig. to elicit no response石沉大海shí chén dà hǎi

to have no news whatever杳无音信yǎo wú yīn xìn

to disappear; to fade away消失xiāo shī

to be gone forever (idiom) · to disappear without a trace杳如黄鹤yǎo rú huáng hè

lit. a clay ox enters the sea (idiom); fig. to disappear with no hope of returning