Must not have

TakaWhat does "must not have+past participle" basically mean?

It is my strong opinion based on solid evidence that X did not occur.

You must not have eaten breakfast. (I know this because you are hungry at 10:00 am.)
She must not have turned off her radio. (I know this because her batteries are dead.)
They must not have turned left at the last intersection. (I know this because they got lost.)
In the affirmative: She must have studied hard, because she got 10/10 on the quiz. They must have left early -

Mister Micawber It is my strong opinion based on solid evidence that X did not occur.

Hey, MM! Long time, no see! How have you been?

The book I have says for such a case, "cannot have+past participle" is used instead of "must not have+past participle."

Do you think in reality both are equally used to mean the same thing?

Based on Philip's additional comments, it seems that "must have+p.p" is used in reality and sounds natural.

Thank you, everyone!

TakaDo you think in reality both are equally used to mean the same thing?

Yes. 'Cannot' is a bit more confident/absolute.

Mister Micawber TakaDo you think in reality both are equally used to mean the same thing?Yes. 'Cannot' is a bit more confident/absolute.

Oh, I thought quite opposite: must not was a bit more confident/absolute. Interesting.

Thanks!

Cliveeg He mustn't've got my message.

He mustn't've gotten my message. (American English)

Indeed.
My version is English English.

TakaThe book I have says for such a case, "cannot have+past participle" is used instead of "must not have+past participle."

I can't remember reading anything about this in a grammar book but my ear would definitely agree with your book.

CB