が置いてある

has been placed

→ が
phrase Rare #34,755
has been placed Describes something that has been placed somewhere and remains there. Often translated as “there is/are ...” when describing what is present in a location.
JA: テーブルの上に花が置いてある。
EN: There are flowers placed on the table.

私の部屋に雑誌が置いてある

There are magazines in my room.

荷物が置いてある場所がない

There’s luggage here, but there’s nowhere to put it.

机の上に本が置いてある

There is a book on the desk.

荷物が置いてある

There’s luggage here.

車の中にが置いてあるんだ

There’s a gun in the car.