残ってた

was left, remained

→ 残る
残っ remain, be left + Te-form (conjunctive) + Past tense
verb · past indicative Rare #38,800
was left, remained Informal contraction of 残っていた.
JA: 冷蔵庫にケーキが残ってた。
EN: There was some cake left in the refrigerator.
Conjugation of 残る
Indicative past
残ってた

まだ誰か残ってた

Was anyone still there?

— オープン・ユア・アイズ (1997)

キャンプでは飲んで記憶は残ってたカリーナパーティーでは記憶が飛んだんだろ

Even when you drank at camp, you still remembered everything. But at Karina’s party, you blacked out, didn’t you?

— Hoje Eu Quero Voltar Sozinho (2014)

サンドイッチどれぐらい残ってた

How many sandwiches were left?

チケットは残ってた

Were there any tickets left?