哎,这是must have done 表推测的用法,表示对过去某事的肯定猜测,译为过去肯定做了某事,其can /could 来表示或疑问形式必须用can /could 来表示
例如
Since the road is wet ,it must have rained last night
只有
He can't have missed the way ,i drew him a map
完全没有你说的那种用法,不存在mustn't have done这个结构,要用can /could 来表示,
不要误人子弟