来てた

had come, was here

→ 来る
来 come; arrive + て Te-form (conjunctive form) + た informal pluperfect ending
verb · informal, pluperfect tense Uncommon #17,345
had come, was here Colloquial contraction of 来ていた.
JA: 友達はもう来てた。
EN: My friend was already here.
Conjugation of 来る
Indicative pluperfect
来てた

来てたのか

Oh, you were here.

— 映画 聲の形 (2016)

君も来てたのか

You came too?

— 8 1/2 (1963)

マイク以外、みんなパーティーに来てたよ。

Everyone came to the party except Mike.

あなたより先にここに来てたのよ。

I got here before you did.

お父さんから手紙は来てた?

Did you get a letter from your dad?

— ラスト、コーション (2007)

あいつはよく俺のところに遊びに来てたんだよ。

He used to come over to my place a lot.

トムは夏になるたびにボストンに来てたよな。

Tom used to come to Boston every summer, didn’t he?

やっぱり先に来てたのね

So you got here before me after all.

— When Marnie Was There (2014)

当時往診に来てた医者が居る

There was a doctor who used to make house calls back then.

— 灼熱の魂 (2010)

彼女は上海に何度か来てたのよ

She had been to Shanghai several times.

— ラスト、コーション (2007)

この間の日曜日、久しぶりにトムが教会に来てたよ。

Tom came to church last Sunday for the first time in a while.

起きたらトムからメール来てた。

When I woke up, I had an email from Tom.