直接引语变间接引语的问题：Mr Lee said:"I haven't been able to find the bo

直接引语变间接引语的问题：Mr Lee said:"I haven't been able to find the book that I lost yeaterday."
请说明原因,
我的答案是Mr Lee said that he hadn't been able to find the book that he had lost the day before。有一点疑虑是如果宾语从句内部两个时态都是过去完成时，那岂不是无法体现动作先后了。