This is the 18815th most frequent Korean word.
실종됐던
"Was missing" or "had disappeared."
The term '실종됐던' here describes a condition in the past where the dog was missing, indicating the closure of its absence.
그의 실종됐던 개가 드디어 돌아왔어요.
His missing dog finally came back.
The usage of '실종됐던' conveys the state of being missing prior to the discovery of the person.
실종됐던 사람은 어제 안전하게 발견되었다.
The person who had gone missing was safely found yesterday.
Here, '실종됐던' reflects a historical event where the ship was lost, contributing to its mythical status.