The clay cow fell into the sea - gone and never returned; no news; gone never to return; never heard from again

Explanation: A clay cow fell into the sea. It is a metaphor that once you leave, you will never come back.

From: Song Dynasty Shi Daoyuan's "Jingde Lantern Record" Volume 8: "I saw two clay cows fighting into the sea, but there is no news until now."