〜と思いきや

Meaning

Expresses surprise that, contrary to what one thought, reality differed from expectation. A somewhat colloquial expression stating that the speaker's prediction was off.

Examples

楽勝だと思いきや、予想外の苦戦を強いられた。 I thought it would be an easy win, but we were forced into an unexpected struggle.
彼はもう帰ったと思いきや、まだ会議室に残っていた。 I thought he had already left, but he was still in the meeting room.
雨が降ると思いきや、午後はすっかり晴れ上がった。 I thought it would rain, but the afternoon cleared up completely.