可以的.

He found himself locked in the room.
是简单句：主语+谓语+宾语+宾补+（地点）状语

He found that he was locked in the room .
是宾语从句,连词that 可以省略.那如果前面有时间状语从句：when he tried to open the door ,he ____________the room.这时还可以填found that he was locked in 吗？还是found that he had been locked in?这个应该是 found that he had been locked in。主句是一般过去时，从句的动作发生在过去的过去，用过去完成时。 当他试图开门时，他发现自己被锁住房间里了。“他被锁住房间里“发生在”他试图开门“之前，而”他试图开门“发生在过去。