walked on the street and could not find my wallet i could ha

walked on the street and could not find my wallet i could have leave it at home
当时我问英语老师为什么是have done 而不是had done 他说情态动词加have done 就是表对过去的推测,但是我觉得有一点问题,求高手解答,贴资料,网址,自己写的也行,但是希望要权威点的