かと思って

thinking that…

→ か
phrase Rare #36,128
thinking that… Often expresses a supposition or expectation, sometimes one that turns out to be mistaken.
JA: 雨が降るかと思って、傘を持ってきた。
EN: I thought it might rain, so I brought an umbrella.

空き家かと思って

I thought it was an abandoned house.

— レベッカ (1940)

君に会えるかと思って外で待っていた。

I waited outside, thinking I might be able to see you.

マジメな質問かと思って…

I thought it was a serious question...

— ビッグ・シック ぼくたちの大いなる目ざめ (2017)

てっきり泥棒かと思って誰だ?

I thought you were a thief. Who are you?

— オープン・ユア・アイズ (1997)