行ってしまっていた

had already gone

→ 行く

phrase Rare #34,122

had already gone Expresses that someone or something had already left or gone by a certain past time. しまう can also add a sense of finality or regret, but here it mainly emphasizes that the departure was already complete.

JA: 駅に着いたとき、電車はもう行ってしまっていた。

EN: When I got to the station, the train had already left.

駅へ着いた時、彼の乗る列車は行ってしまっていた。

When he arrived at the station, the train he was supposed to take had already left.

私が停留所に着いたときには、最終バスはもう行ってしまっていた。

By the time I got to the bus stop, the last bus had already left.

当時は外国へ行ってしまっていたのを知らなかったのですか。

Didn't you know that they had gone abroad by then?

私が目を覚ますと、彼はもう行ってしまっていた。

When I woke up, he had already left.

当時彼は外国へ行ってしまっていたのを知らなかったのですか。

Didn't you know that he had gone abroad by then?