But you are still building on what Scripture doesn't say ANYWHERE. If what you say is true, then why wouldn't she have said, "how can this be since I have pledged myself to God to be a virgin all my life?" Why would she allow herself to be betroathed? If she were dedicated to God alone, why would she become some man's wife and allow her attention to be swallowed up in her relationship with him?
As Paul says: 1 Corinthians 7:34
There is difference also between a wife and a virgin. The unmarried woman careth for the things of the Lord, that she may be holy both in body and in spirit: but she that is married careth for the things of the world, how she may please her husband
Of course, in this context virgin is better understood as unmarried woman since Mary was Joseph's espoused WIFE and still a virgin. But Jewish law and Christian instruction indicated that one shouldn't avoid sexual relations with their spouse except for short periods of time for specific spiritual purposes.
1 Corinthians 7:3-5
3Let the husband render unto the wife due benevolence: and likewise also the wife unto the husband.
4The wife hath not power of her own body, but the husband: and likewise also the husband hath not power of his own body, but the wife.
5Defraud ye not one the other, except it be with consent for a time, that ye may give yourselves to fasting and prayer; and come together again, that Satan tempt you not for your incontinency.
The contention is that this is what is conveyed by "I know not man". Why St. Luke did not elaborate is a good question, but a similar elaboration is missing on the essentials of the Faith, such as the Trinity, -- the stone of stumbling of the early Church or the exact relationship between the works and the faith, which putatively caused the Reformation. However, the rough outline for the need of "josephine" marriage is known from tradition and is reflected in the Protoevangelium of James: that a temple virgin would have to be married off to a suitable man who would take care of her economic life in a patriarchic society without a carnal aspect normally associated with marriage. Since temple virgins were few, the scripture does not deal with regulating the aspects of such marriages.