新概念第二册第18课最后一句话不解

新概念第二册第18课最后一句话不解
After I had had lunch at a village pub, I looked for my bag.
我在一家乡村小酒店吃过午饭后,就找我的提包.
I had left it on a chair beside the door and now it wasn't there!
我曾把它放在门边的椅子上,可这会儿不见了!
As I was looking for it, the landlord came in.
当我正在寻找时,酒店老板走了进来.
'Did you have a good meal?' he asked.
“您吃得好吗?”他问.
'Yes, thank you,' I answered, 'but I can't pay the bill. I haven't got my bag.'
“很好,谢谢.”我回答,“但我付不了帐,我的提包没有了.”
The landlord smiled and immediately went out.
酒店老板笑了笑,马上走了出去.
In a few minutes he returned with my bag and gave it back to me.
一会儿工夫他拿着我的提包回来了,把它还给了我.
'I'm very sorry,' he said. 'My dog had taken it into the garden. He often does this!'
“实在抱歉,”他说,“我的狗把它弄到花园里去了,他常干这种事!”
为什么最后一句诗My dog 【had】 taken it into the garden 而不是用have呢? 不是应该用现在完成时吗 had done 不是说过去的过去吗? 这个明明就是过去啊