だと思ってた

I thought it was

→ だ
phrase Rare #25,512
I thought it was A casual contraction of だと思っていた, expressing a past belief or assumption. The subject and tense may change the English translation depending on context.
JA: 今日は休みだと思ってた。
EN: I thought today was a day off.

彼女は、私が医者だと思ってたのよ。

She thought I was a doctor.

ずっと前、犬は全部オスで、猫は全部メスだと思ってた。

A long time ago, I thought all dogs were male and all cats were female.

トムは医者だと思ってた。

I thought Tom was a doctor.

あいつは千草だと思ってたけどな

I thought that guy was Chigusa, though.

— バトル・ロワイアル (2000)

「君は日本人だと思ってた」「違うよ、僕はメキシコ人さ」

“I thought you were Japanese.” “No, I’m Mexican.”

みんな私のパーティーに来るつもりなのだと思ってた。

I thought everyone was planning to come to my party.

あなたの仕事だと思ってた。

I thought it was your job.

リュウはまあまあだと思ってたが

I thought Ryu was pretty decent, but...

— イップ・マン 序章 (2008)